Related
My server runs CentOS 6.4 with MySQL 5.1.69 installed using yum with CentOS's repos, and PHP 5.4.16 installed using yum with ius's repos. Edit3 Upgraded to MySQL Server version: 5.5.31 Distributed by The IUS Community Project, and error still exists. Then changed library to mysqlnd, and seems to eliminate the error. Still, with this back and forth, need to know why this error only sometimes manifests.
When using PDO and creating the PDO object using PDO::ATTR_EMULATE_PREPARES=>false, I sometimes get the following error:
Table Name - zipcodes
Error in query:
SELECT id FROM cities WHERE name=? AND states_id=?
SQLSTATE[HY000]: General error: 2014 Cannot execute queries while other unbuffered queries are active. Consider using PDOStatement::fetchAll(). Alternatively, if your code is only ever going to run against mysql, you may enable query buffering by setting the PDO::MYSQL_ATTR_USE_BUFFERED_QUERY attribute.
File Name: /var/www/initial_install/build_database.php
Line: 547
Time of Error: Tuesday July 2, 2013, 5:52:48 PDT
Line 547 is the last line of:
$stmt_check_county->execute(array($data[5],$data[4]));
if(!$county_id=$stmt_check_county->fetchColumn())
{
$stmt_counties->execute(array($data[5]));
$county_id=db::db()->lastInsertId();
}
//$stmt_check_county->closeCursor(); //This will fix the error
$stmt_check_city->execute(array($data[3],$data[4]));
I had a similar problem several years ago, but upgraded from PHP 5.1 to PHP 5.3 (and MySQL probably was updated as well), and the problem magically went away, and now I have it with PHP 5.5.
Why does it only manifest itself when PDO::ATTR_EMULATE_PREPARES=>false, and with only alternating version of PHPs?
I've also found that closeCursor() will also fix the error. Should this always be done after every SELECT query where fetchAll() is not used? Note that the error still occurs even if the query is something like SELECT COUNT(col2) which only returns one value.
Edit By the way, this is how I create my connection. I've only recently added MYSQL_ATTR_USE_BUFFERED_QUERY=>true, however, it doesn't cure the error. Also, the following script could be used as is to create the error.
function sql_error($e,$sql=NULL){return('<h1>Error in query:</h1><p>'.$sql.'</p><p>'.$e->getMessage().'</p><p>File Name: '.$e->getFile().' Line: '.$e->getLine().'</p>');}
class db {
private static $instance = NULL;
private function __construct() {} //Make private
private function __clone(){} //Make private
public static function db() //Get instance of DB
{
if (!self::$instance)
{
//try{self::$instance = new PDO("mysql:host=localhost;dbname=myDB;charset=utf8",'myUsername','myPassword',array(PDO::ATTR_EMULATE_PREPARES=>false,PDO::ATTR_ERRMODE=>PDO::ERRMODE_EXCEPTION,PDO::ATTR_DEFAULT_FETCH_MODE=>PDO::FETCH_ASSOC));}
try{self::$instance = new PDO("mysql:host=localhost;dbname=myDB;charset=utf8",'myUsername','myPassword',array(PDO::ATTR_EMULATE_PREPARES=>false,PDO::MYSQL_ATTR_USE_BUFFERED_QUERY=>true,PDO::ATTR_ERRMODE=>PDO::ERRMODE_EXCEPTION,PDO::ATTR_DEFAULT_FETCH_MODE=>PDO::FETCH_ASSOC));}
//try{self::$instance = new PDO("mysql:host=localhost;dbname=myDB;charset=utf8",'myUsername','myPassword',array(PDO::ATTR_ERRMODE=>PDO::ERRMODE_EXCEPTION,PDO::ATTR_DEFAULT_FETCH_MODE=>PDO::FETCH_ASSOC));}
catch(PDOException $e){echo(sql_error($e));}
}
return self::$instance;
}
}
$row=array(
'zipcodes_id'=>'55555',
'cities_id'=>123
);
$data=array($row,$row,$row,$row);
$sql = 'CREATE TEMPORARY TABLE temp1(temp_id INT UNSIGNED NOT NULL AUTO_INCREMENT, PRIMARY KEY (temp_id) )';
db::db()->exec($sql);
$sql='SELECT COUNT(*) AS valid FROM cities_has_zipcodes WHERE cities_id=? AND zipcodes_id=?';
$stmt1 = db::db()->prepare($sql);
$sql ='SELECT temp_id FROM temp1';
$stmt2 = db::db()->prepare($sql);
foreach($data AS $row)
{
try
{
$stmt1->execute(array($row['zipcodes_id'],$row['cities_id']));
$rs1 = $stmt1->fetch(PDO::FETCH_ASSOC);
//$stmt1->closeCursor();
syslog(LOG_INFO,'$rs1: '.print_r($rs1,1).' '.rand());
$stmt2->execute();
$rs2 = $stmt2->fetch(PDO::FETCH_ASSOC);
syslog(LOG_INFO,'$rs2: '.print_r($rs2,1).' '.rand());
}
catch(PDOException $e){echo(sql_error($e));}
}
echo('done');
The MySQL client protocol doesn't allow more than one query to be "in progress." That is, you've executed a query and you've fetched some of the results, but not all -- then you try to execute a second query. If the first query still has rows to return, the second query gets an error.
Client libraries get around this by fetching all the rows of the first query implicitly upon first fetch, and then subsequent fetches simply iterate over the internally cached results. This gives them the opportunity to close the cursor (as far as the MySQL server is concerned). This is the "buffered query." This works the same as using fetchAll(), in that both cases must allocate enough memory in the PHP client to hold the full result set.
The difference is that a buffered query holds the result in the MySQL client library, so PHP can't access the rows until you fetch() each row sequentially. Whereas fetchAll() immediately populates a PHP array for all the results, allowing you access any random row.
The chief reason not to use fetchAll() is that a result might be too large to fit in your PHP memory_limit. But it appears your query results have just one row anyway, so that shouldn't be a problem.
You can closeCursor() to "abandon" a result before you've fetched the last row. The MySQL server gets notified that it can discard that result on the server side, and then you can execute another query. You shouldn't closeCursor() until you're done fetching a given result set.
Also: I notice you're executing your $stmt2 over and over inside the loop, but it will return the same result each time. On the principle of moving loop-invariant code out of the loop, you should have executed this once before starting the loop, and saved the result in a PHP variable. So regardless of using buffered queries or fetchAll(), there's no need for you to nest your queries.
So I would recommend writing your code this way:
$sql ='SELECT temp_id FROM temp1';
$stmt2 = db::db()->prepare($sql);
$stmt2->execute();
$rs2 = $stmt2->fetchAll(PDO::FETCH_ASSOC);
$stmt2->closeCursor();
$sql='SELECT COUNT(*) AS valid FROM cities_has_zipcodes
WHERE cities_id=:cities_id AND zipcodes_id=:zipcodes_id';
$stmt1 = db::db()->prepare($sql);
foreach($data AS $row)
{
try
{
$stmt1->execute($row);
$rs1 = $stmt1->fetchAll(PDO::FETCH_ASSOC);
$stmt1->closeCursor();
syslog(LOG_INFO,'$rs1: '.print_r($rs1[0],1).' '.rand());
syslog(LOG_INFO,'$rs2: '.print_r($rs2[0],1).' '.rand());
}
catch(PDOException $e){echo(sql_error($e));}
}
Note I also used named parameters instead of positional parameters, which makes it simpler to pass $row as the array of parameter values. If the keys of the array match the parameter names, you can just pass the array. In older versions of PHP you had to include the : prefix in the array keys, but you don't need that anymore.
You should use mysqlnd anyway. It has more features, it's more memory-efficient, and its license is compatible with PHP.
I am hoping for a better answer than the following. While some of these solutions might "fix" the problem, they don't answer the original question regarding what causes this error.
Set PDO::ATTR_EMULATE_PREPARES=>true (I don't wish to do this)
Set PDO::MYSQL_ATTR_USE_BUFFERED_QUERY (didn't work for me)
Use PDOStatement::fetchAll() (not always desirable)
Use $stmt->closeCursor() after each $stmt->fetch() (this mostly worked, however, I still had several cases where it didn't)
Change PHP MySQL library from php-mysql to php-mysqlnd (probably what I will do if no better answer)
I have almost same problem. My first query after connection to db return empty result and drop this error. Enabling buffer doesn't help.
My connection code was:
try {
$DBH = new PDO("mysql:host=$hostname;dbname=$db_name", $username, $password,
array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET CHARACTER SET utf8; SET NAMES utf8",
PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_NUM));
}
catch(PDOException $e) { echo $e->getMessage(); }
Solution in my way was to remove initial command:
PDO::MYSQL_ATTR_INIT_COMMAND => "SET CHARACTER SET utf8; SET NAMES utf8"
Here is a correct code:
try {
$DBH = new PDO("mysql:host=$hostname;dbname=$db_name", $username, $password,
array(PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_NUM));
}
catch(PDOException $e) { echo $e->getMessage(); }
And MYSQL_ATTR_USE_BUFFERED_QUERY is not forced to true. It's set as default.
I also experienced this problem today and noticed that I put wrong SQL statement (SELECT) into PDO's exec() method. Then I came to a conclusion that we can only put write (INSERT, UPDATE, DELETE) SQL statements instead of read (SELECT) ones to the method.
!!!
WARNING !!!
This can also happen if you are trying to fetch a non SELECT query (Eg - UPDATE/INSERT/ALTER/CREATE)
if anybody is here, with error while creating tables
this also happens if you try to execute create 2 tables in single query;
this error was thrown when i fired below query;
$q24="create table if not exists table1 like template1;create table if not exists table2 like template2;";
$s24=$link->prepare($q24);
$s24->execute();
seems tables are to be created separately;
$q1="create table if not exists table1 like template1;";
$s1=$link->prepare($q1);
$s1->execute();
//and
$q2="create table if not exists table2 like template2;";
$s2=$link->prepare($q2);
$s2->execute();
I had the same problem, I was sending results to another function mid loop. Quick fix was, save all results in an array (like Bill stated, if it's too large you have other issues to worry about), after collecting the data, I ran a separate loop to call the function one at a time.
Also, PDO::MYSQL_ATTR_USE_BUFFERED_QUERY did not work for me.
I had the same problem and solved it by removing all initial requests related to the character set.
so I started from
$con = new \PDO(self::getDriver() . ":host=" . self::getHost() . ":".self::getPort()."; dbname=" . self::getName() . ";charset=utf8", self::getUser(), self::getPassword(), array( \PDO::MYSQL_ATTR_USE_BUFFERED_QUERY => true,\PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8;SET SESSION time_zone ='+01:00'"));
to
$con = new \PDO(self::getDriver() . ":host=" . self::getHost() . ":".self::getPort()."; dbname=" . self::getName() . ";charset=utf8", self::getUser(), self::getPassword(), array( \PDO::MYSQL_ATTR_USE_BUFFERED_QUERY => true,\PDO::MYSQL_ATTR_INIT_COMMAND => "SET SESSION time_zone ='+01:00'"));
so I removed the command SET NAMES utf8;
I got this error when I accidentally called execute twice, one explicitly and one that was hidden in another call (PDO class).
After removing the first execute, the error was gone.
The main reason behind this error is that MySQL is trying to run 'exec' instead of 'execute' and vice versa.
There are two PDO statements that are there to execute queries PDO::exec() and PDO::execute(), both are not the same.
PDO::exec() is designed to execute commands and queries that do not produce a result set.
Ex: SET, UPDATE, INSERT, DELETE etc.
PDO::execute() is designed to execute commands and queries that produce a result set.
Ex: SELECT, CALL, SHOW, OPTIMIZE, EXPLAIN etc.
If you use these commands in wrong place, your will be ended up with this error.
Solution:
Be careful where to use PDO::exec() and PDO::execute()
In my case for Laravel I changed my query from
DB::select("DELETE FROM " . env('DB_PREFIX') . 'products WHERE
product_id = ' . $product->id); // Internally Laravel will run PDO::execute()
'select' method
to
DB::table('product_currency')->where('product_id',
$product->id)->delete(); // Internally Laravel will run PDO::exec()
Hope this gives some more clarification!
My server runs CentOS 6.4 with MySQL 5.1.69 installed using yum with CentOS's repos, and PHP 5.4.16 installed using yum with ius's repos. Edit3 Upgraded to MySQL Server version: 5.5.31 Distributed by The IUS Community Project, and error still exists. Then changed library to mysqlnd, and seems to eliminate the error. Still, with this back and forth, need to know why this error only sometimes manifests.
When using PDO and creating the PDO object using PDO::ATTR_EMULATE_PREPARES=>false, I sometimes get the following error:
Table Name - zipcodes
Error in query:
SELECT id FROM cities WHERE name=? AND states_id=?
SQLSTATE[HY000]: General error: 2014 Cannot execute queries while other unbuffered queries are active. Consider using PDOStatement::fetchAll(). Alternatively, if your code is only ever going to run against mysql, you may enable query buffering by setting the PDO::MYSQL_ATTR_USE_BUFFERED_QUERY attribute.
File Name: /var/www/initial_install/build_database.php
Line: 547
Time of Error: Tuesday July 2, 2013, 5:52:48 PDT
Line 547 is the last line of:
$stmt_check_county->execute(array($data[5],$data[4]));
if(!$county_id=$stmt_check_county->fetchColumn())
{
$stmt_counties->execute(array($data[5]));
$county_id=db::db()->lastInsertId();
}
//$stmt_check_county->closeCursor(); //This will fix the error
$stmt_check_city->execute(array($data[3],$data[4]));
I had a similar problem several years ago, but upgraded from PHP 5.1 to PHP 5.3 (and MySQL probably was updated as well), and the problem magically went away, and now I have it with PHP 5.5.
Why does it only manifest itself when PDO::ATTR_EMULATE_PREPARES=>false, and with only alternating version of PHPs?
I've also found that closeCursor() will also fix the error. Should this always be done after every SELECT query where fetchAll() is not used? Note that the error still occurs even if the query is something like SELECT COUNT(col2) which only returns one value.
Edit By the way, this is how I create my connection. I've only recently added MYSQL_ATTR_USE_BUFFERED_QUERY=>true, however, it doesn't cure the error. Also, the following script could be used as is to create the error.
function sql_error($e,$sql=NULL){return('<h1>Error in query:</h1><p>'.$sql.'</p><p>'.$e->getMessage().'</p><p>File Name: '.$e->getFile().' Line: '.$e->getLine().'</p>');}
class db {
private static $instance = NULL;
private function __construct() {} //Make private
private function __clone(){} //Make private
public static function db() //Get instance of DB
{
if (!self::$instance)
{
//try{self::$instance = new PDO("mysql:host=localhost;dbname=myDB;charset=utf8",'myUsername','myPassword',array(PDO::ATTR_EMULATE_PREPARES=>false,PDO::ATTR_ERRMODE=>PDO::ERRMODE_EXCEPTION,PDO::ATTR_DEFAULT_FETCH_MODE=>PDO::FETCH_ASSOC));}
try{self::$instance = new PDO("mysql:host=localhost;dbname=myDB;charset=utf8",'myUsername','myPassword',array(PDO::ATTR_EMULATE_PREPARES=>false,PDO::MYSQL_ATTR_USE_BUFFERED_QUERY=>true,PDO::ATTR_ERRMODE=>PDO::ERRMODE_EXCEPTION,PDO::ATTR_DEFAULT_FETCH_MODE=>PDO::FETCH_ASSOC));}
//try{self::$instance = new PDO("mysql:host=localhost;dbname=myDB;charset=utf8",'myUsername','myPassword',array(PDO::ATTR_ERRMODE=>PDO::ERRMODE_EXCEPTION,PDO::ATTR_DEFAULT_FETCH_MODE=>PDO::FETCH_ASSOC));}
catch(PDOException $e){echo(sql_error($e));}
}
return self::$instance;
}
}
$row=array(
'zipcodes_id'=>'55555',
'cities_id'=>123
);
$data=array($row,$row,$row,$row);
$sql = 'CREATE TEMPORARY TABLE temp1(temp_id INT UNSIGNED NOT NULL AUTO_INCREMENT, PRIMARY KEY (temp_id) )';
db::db()->exec($sql);
$sql='SELECT COUNT(*) AS valid FROM cities_has_zipcodes WHERE cities_id=? AND zipcodes_id=?';
$stmt1 = db::db()->prepare($sql);
$sql ='SELECT temp_id FROM temp1';
$stmt2 = db::db()->prepare($sql);
foreach($data AS $row)
{
try
{
$stmt1->execute(array($row['zipcodes_id'],$row['cities_id']));
$rs1 = $stmt1->fetch(PDO::FETCH_ASSOC);
//$stmt1->closeCursor();
syslog(LOG_INFO,'$rs1: '.print_r($rs1,1).' '.rand());
$stmt2->execute();
$rs2 = $stmt2->fetch(PDO::FETCH_ASSOC);
syslog(LOG_INFO,'$rs2: '.print_r($rs2,1).' '.rand());
}
catch(PDOException $e){echo(sql_error($e));}
}
echo('done');
The MySQL client protocol doesn't allow more than one query to be "in progress." That is, you've executed a query and you've fetched some of the results, but not all -- then you try to execute a second query. If the first query still has rows to return, the second query gets an error.
Client libraries get around this by fetching all the rows of the first query implicitly upon first fetch, and then subsequent fetches simply iterate over the internally cached results. This gives them the opportunity to close the cursor (as far as the MySQL server is concerned). This is the "buffered query." This works the same as using fetchAll(), in that both cases must allocate enough memory in the PHP client to hold the full result set.
The difference is that a buffered query holds the result in the MySQL client library, so PHP can't access the rows until you fetch() each row sequentially. Whereas fetchAll() immediately populates a PHP array for all the results, allowing you access any random row.
The chief reason not to use fetchAll() is that a result might be too large to fit in your PHP memory_limit. But it appears your query results have just one row anyway, so that shouldn't be a problem.
You can closeCursor() to "abandon" a result before you've fetched the last row. The MySQL server gets notified that it can discard that result on the server side, and then you can execute another query. You shouldn't closeCursor() until you're done fetching a given result set.
Also: I notice you're executing your $stmt2 over and over inside the loop, but it will return the same result each time. On the principle of moving loop-invariant code out of the loop, you should have executed this once before starting the loop, and saved the result in a PHP variable. So regardless of using buffered queries or fetchAll(), there's no need for you to nest your queries.
So I would recommend writing your code this way:
$sql ='SELECT temp_id FROM temp1';
$stmt2 = db::db()->prepare($sql);
$stmt2->execute();
$rs2 = $stmt2->fetchAll(PDO::FETCH_ASSOC);
$stmt2->closeCursor();
$sql='SELECT COUNT(*) AS valid FROM cities_has_zipcodes
WHERE cities_id=:cities_id AND zipcodes_id=:zipcodes_id';
$stmt1 = db::db()->prepare($sql);
foreach($data AS $row)
{
try
{
$stmt1->execute($row);
$rs1 = $stmt1->fetchAll(PDO::FETCH_ASSOC);
$stmt1->closeCursor();
syslog(LOG_INFO,'$rs1: '.print_r($rs1[0],1).' '.rand());
syslog(LOG_INFO,'$rs2: '.print_r($rs2[0],1).' '.rand());
}
catch(PDOException $e){echo(sql_error($e));}
}
Note I also used named parameters instead of positional parameters, which makes it simpler to pass $row as the array of parameter values. If the keys of the array match the parameter names, you can just pass the array. In older versions of PHP you had to include the : prefix in the array keys, but you don't need that anymore.
You should use mysqlnd anyway. It has more features, it's more memory-efficient, and its license is compatible with PHP.
I am hoping for a better answer than the following. While some of these solutions might "fix" the problem, they don't answer the original question regarding what causes this error.
Set PDO::ATTR_EMULATE_PREPARES=>true (I don't wish to do this)
Set PDO::MYSQL_ATTR_USE_BUFFERED_QUERY (didn't work for me)
Use PDOStatement::fetchAll() (not always desirable)
Use $stmt->closeCursor() after each $stmt->fetch() (this mostly worked, however, I still had several cases where it didn't)
Change PHP MySQL library from php-mysql to php-mysqlnd (probably what I will do if no better answer)
I have almost same problem. My first query after connection to db return empty result and drop this error. Enabling buffer doesn't help.
My connection code was:
try {
$DBH = new PDO("mysql:host=$hostname;dbname=$db_name", $username, $password,
array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET CHARACTER SET utf8; SET NAMES utf8",
PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_NUM));
}
catch(PDOException $e) { echo $e->getMessage(); }
Solution in my way was to remove initial command:
PDO::MYSQL_ATTR_INIT_COMMAND => "SET CHARACTER SET utf8; SET NAMES utf8"
Here is a correct code:
try {
$DBH = new PDO("mysql:host=$hostname;dbname=$db_name", $username, $password,
array(PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_NUM));
}
catch(PDOException $e) { echo $e->getMessage(); }
And MYSQL_ATTR_USE_BUFFERED_QUERY is not forced to true. It's set as default.
I also experienced this problem today and noticed that I put wrong SQL statement (SELECT) into PDO's exec() method. Then I came to a conclusion that we can only put write (INSERT, UPDATE, DELETE) SQL statements instead of read (SELECT) ones to the method.
!!!
WARNING !!!
This can also happen if you are trying to fetch a non SELECT query (Eg - UPDATE/INSERT/ALTER/CREATE)
if anybody is here, with error while creating tables
this also happens if you try to execute create 2 tables in single query;
this error was thrown when i fired below query;
$q24="create table if not exists table1 like template1;create table if not exists table2 like template2;";
$s24=$link->prepare($q24);
$s24->execute();
seems tables are to be created separately;
$q1="create table if not exists table1 like template1;";
$s1=$link->prepare($q1);
$s1->execute();
//and
$q2="create table if not exists table2 like template2;";
$s2=$link->prepare($q2);
$s2->execute();
I had the same problem, I was sending results to another function mid loop. Quick fix was, save all results in an array (like Bill stated, if it's too large you have other issues to worry about), after collecting the data, I ran a separate loop to call the function one at a time.
Also, PDO::MYSQL_ATTR_USE_BUFFERED_QUERY did not work for me.
I had the same problem and solved it by removing all initial requests related to the character set.
so I started from
$con = new \PDO(self::getDriver() . ":host=" . self::getHost() . ":".self::getPort()."; dbname=" . self::getName() . ";charset=utf8", self::getUser(), self::getPassword(), array( \PDO::MYSQL_ATTR_USE_BUFFERED_QUERY => true,\PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8;SET SESSION time_zone ='+01:00'"));
to
$con = new \PDO(self::getDriver() . ":host=" . self::getHost() . ":".self::getPort()."; dbname=" . self::getName() . ";charset=utf8", self::getUser(), self::getPassword(), array( \PDO::MYSQL_ATTR_USE_BUFFERED_QUERY => true,\PDO::MYSQL_ATTR_INIT_COMMAND => "SET SESSION time_zone ='+01:00'"));
so I removed the command SET NAMES utf8;
I got this error when I accidentally called execute twice, one explicitly and one that was hidden in another call (PDO class).
After removing the first execute, the error was gone.
The main reason behind this error is that MySQL is trying to run 'exec' instead of 'execute' and vice versa.
There are two PDO statements that are there to execute queries PDO::exec() and PDO::execute(), both are not the same.
PDO::exec() is designed to execute commands and queries that do not produce a result set.
Ex: SET, UPDATE, INSERT, DELETE etc.
PDO::execute() is designed to execute commands and queries that produce a result set.
Ex: SELECT, CALL, SHOW, OPTIMIZE, EXPLAIN etc.
If you use these commands in wrong place, your will be ended up with this error.
Solution:
Be careful where to use PDO::exec() and PDO::execute()
In my case for Laravel I changed my query from
DB::select("DELETE FROM " . env('DB_PREFIX') . 'products WHERE
product_id = ' . $product->id); // Internally Laravel will run PDO::execute()
'select' method
to
DB::table('product_currency')->where('product_id',
$product->id)->delete(); // Internally Laravel will run PDO::exec()
Hope this gives some more clarification!
I've been playing around with switching over to the PDO way of doing database work in PHP. In my java life, I am able to place named queries into an associative array and call the prepared statement using the index. It's a bit more complex than that, but...
Anyways I thought it would be cool to do the same type of thing in PHP.
$NamedQueries['SelectBlackBoxById'] = "select name, category, rating from blackbox where id = :blackbox_id";
So I can prepare my statements this way:
$sth = $dbh->prepare($NamedQueries['SelectBlackBoxById']);
$sth->execute(array('blackbox_id' => '1'));
$sth->setFetchMode(PDO::FETCH_OBJ);
return $sth->fetch();
Instead of this way:
$sth = $dbh->prepare("select name, category, rating from blackbox where id = :blackbox_id");
$sth->execute(array('blackbox_id' => '1'));
$sth->setFetchMode(PDO::FETCH_OBJ);
return $sth->fetch();
I'm sure I am overlooking something, because my preferred way returns false. Any ideas would be greatly appreciated.
$sth->execute(array('blackbox_id' => '1'));
Should be
$sth->execute(array(':blackbox_id' => '1'));
You have to include the :
Did you try to dump out your Array value before you use it to prepare the query?
Overall, I don't see anything wrong with how the PDO would use it, you could also var_dump() your $sth variable after you prepare it to see what might be in there.
In general, as others pointed out the ':' is something you should include when you bind variables, although in this case I don't necessarily think it is the root problem as you said your second example worked, which uses the same syntax, the only difference is using the query from the array instead of a raw string. Thinking that since it is only 1 variable to bind, not having the ':' is not causing problems (though you should add it)
So, your real problem is lack of error handling. And it persists.
error_reporting(E_ALL);
to be notified of variables that out of scope.
$dbh->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
after connect to be notified of empty queries and whatever else PDO errors
I am attempting to get the following PDO statement to work and running into issues. When I am trying to get the number of rows, I keep getting 0, yet I know there should be 1 row. When I ran it as a mysqli statement( before trying to change it to PDO) it worked perfectly.
Here is the code:
require_once ('pdo.php');
$isbn = $_POST['isbn'];
// check to see if the isbn is a "problem" isbn or not
$problem = $conn->prepare("select isbn, note from problem where isbn = :isbn");
$problem->bindParam(":isbn", $isbn);
$problem->execute();
print_r($problem);
$num_rows = $problem->rowCount();
print_r($num_rows); die;
EDIT: Here is pdo.php:
<?php
function db_connect()
{
$db = new PDO("mysql:host=localhost; db=bookcell_BCOS_final", "xxxxx", "xxxxx");
return($db);
}
?>
I know that my connection works, but I get 0 for $num_rows. What mistakes am I making here?
Besides a little quirk and a optimalisation your code looks fine to me. The posted value isbn could be the reasong that you are getting no data:
$problem = $conn->prepare("select isbn, note from problem where isbn = :isbn");
$problem->bindParam(":isbn", $_POST['isbn'], PDO::PARAM_STR); // <-- thats what parameter binding is for
$problem->execute();
print_r($problem);
$num_rows = $problem->rowCount(); // <-- gives the number of rows, not columnCOunt
print_r($num_rows); die;
The Syntax for $num_rows = $problem->columnCount(); is totally correct. You may try,
$problem->execute(array("isbn" => $isbn));
instead of bindParam.
for getting the no. of rows, you need to use pdo::rowCount() -- manual here
In PDO to verfiy if your execute statement did work, check the return value (bool):
$success = $problem->execute();
if (!$success) {
$arr = $problem->errorInfo();
print_r($arr);
}
Also you might be looking for rowCount() instead of columnCount() but I think the error handling is your furthermost issue.
Additionally you can make PDO throw an exception each time an error appears, compare:
Switching from PHP's mysql extension to PDO. Extend class to reduce lines of code
How do I raise PDOException?
Depending on the database driver and the mode it's running, PDO may not be able to give you a row count. Look carefully at the documentation for PDOStatement::rowCount():
If the last SQL statement executed by the associated PDOStatement was a SELECT statement, some databases may return the number of rows returned by that statement. However, this behaviour is not guaranteed for all databases and should not be relied on for portable applications.
This is because in many cases the database uses a cursor rather than fetching the full results and buffering them (which is how the old mysql_* functions behave). In this case the database doesn't know how many rows there are until you have looked at all the rows. Think of a cursor as something like a filesystem pointer--you can't know the filesize until you seek to the end of the file.
I know this question has been asked many times, but I've read the answers to many of the questions and still cannot understand why I am receiving this error:
Fatal error: Uncaught exception 'PDOException' with message
'SQLSTATE[HY000]: General error: 2014 Cannot execute queries while
other unbuffered queries are active. Consider using
PDOStatement::fetchAll(). Alternatively, if your code is only ever
going to run against mysql, you may enable query buffering by setting
the PDO::MYSQL_ATTR_USE_BUFFERED_QUERY attribute.'
The first thing that is odd, is that I do not get an error on my localhost (wampserver), but I do get it on my web server. The php version on my localhost is 5.3.10, and on my web server it is 5.3.13.
I have read that the source of this error is making a query when data left in the buffer from a previous query. This is not the case for me -- I have echo'd out all of the data and I know for a fact that every row returned in a query is being fetched.
With that said, I have found that changing one of my queries to fetchAll instead of fetch fixes the problem, but it simply makes no since because I know that all of the rows returned are being read. When I used fetchAll for the query (it is being made in a loop), I printed out the array each loop, and only one item was in the array for each query in the loop.
One more piece of information. It's not the query that I changed to fetchAll (which makes the error go away) that throws the PDO error, there is another query later in my php file that throws the error. My file is basically like this:
... code ...
query 1
... code ...
loop
query 2
end loop
... code ...
query 3
If I comment out query 3, there is no error. If I comment out, or change to fetchAll, query 2, there is no error. query 1 has no affect whatsoever.
I would also like to add that I have tried adding LIMIT 1 to all of the queries on the page (at the same time), and the error is still there. I think this proves there is not unread data in the buffer, right?
I'm really confused, so I would appreciate your advice. Before someone asks, I can't post the full code for this, but here is a simplified version of my code:
$stmt = $this->db->prepare('SELECT ... :par LIMIT 1');
makeQuery($stmt, array(':par' => $var));
$row = $stmt->fetch(PDO::FETCH_ASSOC);
$stmt = $this->db->prepare('SELECT ... :par LIMIT 1');
for loop
makeQuery($stmt, array(':par' => $var));
$row2 = $stmt->fetch(PDO::FETCH_ASSOC);
... [use row2] ...
end for loop
$stmt = $this->db->prepare('SELECT ... :par LIMIT 1');
makeQuery($stmt, array(':par' => $var));
$row3 = $stmt->fetch(PDO::FETCH_ASSOC);
Here is makeQuery().
/**************************************************************************************************************
* Function: makeQuery *
* Desc: Makes a PDO query. *
* Pre conditions: The statement/query and an array of named parameters (may be empty) must be passed. *
* Post conditions: The PDO query is executed. Exceptions are caught, displayed, and page execution stopped. *
**************************************************************************************************************/
function makeQuery($stmt, $array, $errMsg = '')
{
try
{
$stmt->execute($array);
}
catch (PDOException $e)
{
print $errMsg != ''?$errMsg:"Error!: " . $e->getMessage() . "<br/>";
die();
}
}
Thanks for your help!
EDIT: I also tried doing the following after query 2 (since that seems to be the source of the problem:
$row2 = $stmt->fetch(PDO::FETCH_ASSOC); var_dump($row2);
The output was:
bool(false)
Have I stumbled across a PDO bug?
You need to fetch until a row fetch attempt fails. I know you may only have one row in the result set and think one fetch is enough, but its not (when you're using unbuffered queries). PDO doesn't know how many rows there are until it reaches the end, where it tries to fetch the next row, but it fails.
You probably have other statements where you didn't fully "fetch until a fetch failed". Yes, I see that you fetch until the fetch failed for one of the statements, but that doesn't mean you did it for all of them.
To clarify -
When you execute a query via execute(), you create a result set that must be fetched from the db into php. PDO can only handle 1 of these "result set in progress of being fetched" at a time (per connection). You need to completely fetch the result set, all the way to the end of it, before you can start fetching a different result set from a different call to execute().
When you "call fetch() until a fetch() fails", the fact that you reached the end of the results is internally noted by PDO when that final call to fetch() fails due to there being no more results. PDO is then satisfied that the results are fully fetched, and it can clean up whatever internal resources between php and the db that were established for that result set, allowing you to make/fetch other queries.
There's other ways to make PDO "call fetch() until a fetch() fails".
Just use fetchAll(), which simply fetches all rows, and so it will hit the end of the result set.
or just call closeCursor()
*if you look at the source for closeCursor(), the default implementation literally just fetches the rows and discards them until it reaches the end. It's written in c obviously, but it more or less does this:
function closeCursor() {
while ($row = $stmt->fetch()) {}
$this->stmtFullyFetched = true;
}
Some db drivers may have a more efficient implementation that doesn't require them to fetch lots of rows that nobody cares about, but that's the default way PDO does it. Anyway...
Normally you don't have these problems when you use buffered queries. The reason is because with buffered queries, right after you execute them, PDO will automatically fully fetch the db results into php memory, so it does the "call fetch() until a fetch() fails" part for you, automatically. When you later call fetch() or fetchAll() yourself, it's fetching results from php memory, not from the db. So basically, the result set is immediately fully fetched when using buffered queries, so there's no opportunity to have more than 1 "result set in progress of being fetched" at the same time (because php is single threaded, so no chance of 2 queries running at the same time).
Given this:
$sql = "select * from test.a limit 1";
$stmt = $dbh->prepare($sql);
$stmt->execute(array());
Ways to fully fetch the result set (assuming you only want the first row):
$row = $stmt->fetch();
$stmt->closeCursor();
or
list($row) = $stmt->fetchAll(); //tricky
or
$row = $stmt->fetch();
while ($stmt->fetch()) {}
After struggling with this issue for days, I finally found that this worked for me:
$db = new PDO ($cnstring, $user, $pwd);
$db->setAttribute (PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, true);
This also happen if you are trying to fetch a non SELECT query (Eg - UPDATE/INSERT/ALTER/CREATE). Make sure to use fetch or fetchAll only for SELECT queries.
Possible Duplicate Answer/Question