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I recently learned about SQL Injection and the PHP recommendation to avoid it, using prepare() and bind_param().
Now, I want to prepare SQL queries dynamically, adding both column names and values.
I usted to do it like this, having the name field of the HTML input with the same name as the MySQL database column.
<input type="text" name="firstname" >
<input type="text" name="lastname" >
And the, create the SQL query dynamically using mysqli.
// Extract values from POST
$parameters = $_POST;
// Organize the values in two strings
foreach ($parameters as $id => $value) {
$fields = $fields . "`" . $id . "`,";
$values = $values . "'" . $value . "',";
/*e.g.
$fields = `firstname`,`lastname`
$values = 'John','Wick'
*/
}
// Write into the database
$sql = "INSERT INTO `user` ($fields) VALUES ($values)";
/*e.g.
INSERT INTO `user` (`firstname`,`lastname`) VALUES ('John','Wick')
*/
I would like to know if there is a way to do this using prepare() and bind_param() to avoid SQL injection, may be adding adding some data-type="s" to the HTML input tag or if there is a better, more best-practices, way to do it.
You can use bound parameters only for an element that would be a constant value — a quoted string, a quoted datetime, or a numeric literal.
You can't use a parameter placeholder for anything else in SQL, like column names, table names, lists of values, SQL keywords or expressions, or other syntax.
If you need to make column names dynamic, the only option is to validate them against a list of known columns.
$columns_in_user_table = [
'userid'=>null,
'username'=>'',
'firstname'=>'',
'lastname'=>''
];
// Extract values from POST, but only those that match known columns
$parameters = array_intersect_key($_POST, $columns_in_user_table);
// Make sure no columns are missing; assign default values as needed
$parameters = array_merge($columns_in_user_table, $parameters);
If you use PDO instead of mysqli, you can skip the binding. Just use named parameters, and pass your associative array of column-value pairs directly to execute():
$columns = [];
$placeholders = [];
foreach ($parameters as $col => $value) {
$columns[] = "`$col`";
$placeholders[] = ":$col";
}
$column_list = implode($columns, ',');
$placeholder_list = implode($placeholders, ',');
// Write into the database
$sql = "INSERT INTO `user` ($column_list) VALUES ($placeholder_list)";
$stmt = $pdo->prepare($sql);
$stmt->execute($parameters);
I noticed you included the mysqli tag on your question, so assuming your database is MySQL and you are using the native MySQL functions, then you can do something like this:
$stmt = mysqli_prepare($link, "INSERT INTO CountryLanguage VALUES (?, ?, ?, ?)");
mysqli_stmt_bind_param($stmt, 'sssd', $code, $language, $official, $percent);
$code = 'DEU';
$language = 'Bavarian';
$official = "F";
$percent = 11.2;
/* execute prepared statement */
mysqli_stmt_execute($stmt);
And yes, I ripped that straight out of the PHP manual page on mysqli_stmt_bind_param.
I'm using this code and I'm beyond frustration:
try {
$dbh = new PDO('mysql:dbname=' . DB . ';host=' . HOST, USER, PASS);
$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$dbh->setAttribute(PDO::MYSQL_ATTR_INIT_COMMAND, "SET NAMES 'utf8'");
}
catch(PDOException $e)
{
...
}
$stmt = $dbh->prepare('INSERT INTO table(v1, v2, ...) VALUES(:v1, :v2, ...)');
$stmt->bindParam(':v1', PDO::PARAM_NULL); // --> Here's the problem
PDO::PARAM_NULL, null, '', all of them fail and throw this error:
Fatal error: Cannot pass parameter 2 by reference in /opt/...
You need to use bindValue, not bindParam
bindParam takes a variable by reference, and doesn't pull in a value at the time of calling bindParam. I found this in a comment on the PHP docs:
bindValue(':param', null, PDO::PARAM_INT);
P.S. You may be tempted to do this bindValue(':param', null, PDO::PARAM_NULL); but it did not work for everybody (thank you Will Shaver for reporting.)
When using bindParam() you must pass in a variable, not a constant. So before that line you need to create a variable and set it to null
$myNull = null;
$stmt->bindParam(':v1', $myNull, PDO::PARAM_NULL);
You would get the same error message if you tried:
$stmt->bindParam(':v1', 5, PDO::PARAM_NULL);
When using INTEGER columns (that can be NULL) in MySQL, PDO has some (to me) unexpected behaviour.
If you use $stmt->execute(Array), you have to specify the literal NULL and cannot give NULL by variable reference.
So this won't work:
// $val is sometimes null, but sometimes an integer
$stmt->execute(array(
':param' => $val
));
// will cause the error 'incorrect integer value' when $val == null
But this will work:
// $val again is sometimes null, but sometimes an integer
$stmt->execute(array(
':param' => isset($val) ? $val : null
));
// no errors, inserts NULL when $val == null, inserts the integer otherwise
Tried this on MySQL 5.5.15 with PHP 5.4.1
For those who still have problems (Cannot pass parameter 2 by reference), define a variable with null value, not just pass null to PDO:
bindValue(':param', $n = null, PDO::PARAM_INT);
Hope this helps.
I had the same problem and I found this solution working with bindParam :
bindParam(':param', $myvar = NULL, PDO::PARAM_INT);
If you want to insert NULL only when the value is empty or '', but insert the value when it is available.
A) Receives the form data using POST method, and calls function insert with those values.
insert( $_POST['productId'], // Will be set to NULL if empty
$_POST['productName'] ); // Will be to NULL if empty
B) Evaluates if a field was not filled up by the user, and inserts NULL if that's the case.
public function insert( $productId, $productName )
{
$sql = "INSERT INTO products ( productId, productName )
VALUES ( :productId, :productName )";
//IMPORTANT: Repace $db with your PDO instance
$query = $db->prepare($sql);
//Works with INT, FLOAT, ETC.
$query->bindValue(':productId', !empty($productId) ? $productId : NULL, PDO::PARAM_INT);
//Works with strings.
$query->bindValue(':productName',!empty($productName) ? $productName : NULL, PDO::PARAM_STR);
$query->execute();
}
For instance, if the user doesn't input anything on the productName field of the form, then $productName will be SET but EMPTY. So, you need check if it is empty(), and if it is, then insert NULL.
Tested on PHP 5.5.17
Good luck,
Several answers have given examples of what you should do. But they haven't really explained why you should do one of those things.
The bindParam method is meant to be used with something like a loop (or just repeated statements). It binds a variable reference. So something like
$stmt = $dbh->prepare('INSERT INTO t1 (v1) VALUES(:v1)');
$stmt->bindParam(':v1', $i, PDO::PARAM_INT);
for ($i = 0; $i < 10; $i++) {
$stmt->execute();
}
Would insert values 0 through 9 in a table.
That's obviously a very simple example that could be implemented in other, more efficient ways. You could have more complex logic here. But the basic idea is that you bind a reference to a variable and then you can change the value of the variable.
You can get around the need for a reference by creating a variable before calling bindParam. But in your case, you don't particularly want to bind to a variable reference. You just want to bind a value. So go ahead and do exactly that with bindValue.
You can mostly just use bindValue. But to show why both methods exist, let's rewrite the previous example to use bindValue instead of bindParam:
$stmt = $dbh->prepare('INSERT INTO t1 (v1) VALUES(:v1)');
for ($i = 0; $i < 10; $i++) {
$stmt->bindValue(':v1', $i, PDO::PARAM_INT);
$stmt->execute();
}
This will work, but you have to call bindValue on every iteration of the loop whereas you only needed to call bindParam once. But you aren't doing anything like that, so you can just
$stmt->bindValue(':v1', null, PDO::PARAM_INT);
And everything will work, as stated in the accepted answer. Because you want to bind a value, not a variable reference.
Based on the other answers but with a little more clarity on how to actually use this solution.
If for example you have an empty string for a time value but you want to save it as a null:
if($endtime == ""){
$db->bind(":endtime",$endtime=NULL,PDO::PARAM_STR);
}else{
$db->bind("endtime",$endtime);
}
Notice that for time values you would use PARAM_STR, as times are stored as strings.
So you just need to add an extra If statement that properly changes your variable to NULL before you call bindParam(). Here is an example that I figured out for my situation (I was stuck on this for days trying to INSERT a new DB record with a NULL value for one column):
if ($this->companyid == 'NULL' || $this->companyid == NULL) {
$this->companyid = NULL;
$this->companyname = NULL;
$stmt->bindParam(':companyid', $this->companyid);
$stmt->bindParam(':companyname', $this->companyname);
} else {
$stmt->bindParam(':companyid', $this->companyid);
$stmt->bindParam(':companyname', $this->companyname);
}
Try This.
$stmt->bindValue(':v1', null, PDO::PARAM_NULL); // --> insert null
In my case I am using:
SQLite,
prepared statements with placeholders to handle unknown number of fields,
AJAX request sent by user where everything is a string and there is no such thing like NULL value and
I desperately need to insert NULLs as that does not violates foreign key constrains (acceptable value).
Suppose, now user sends with post: $_POST[field1] with value value1 which can be the empty string "" or "null" or "NULL".
First I make the statement:
$stmt = $this->dbh->prepare("INSERT INTO $table ({$sColumns}) VALUES ({$sValues})");
where {$sColumns} is sth like field1, field2, ... and {$sValues} are my placeholders ?, ?, ....
Then, I collect my $_POST data related with the column names in an array $values and replace with NULLs:
for($i = 0; $i < \count($values); $i++)
if((\strtolower($values[$i]) == 'null') || ($values[$i] == ''))
$values[$i] = null;
Now, I can execute:
$stmt->execute($values);
and among other bypass foreign key constrains.
If on the other hand, an empty string does makes more sense then you have to check if that field is part of a foreign key or not (more complicated).
I am inserting the $_POST contents of my PHP array into a table with PDO. I was looking at the following lines of code and I had one of those "there has to be a better way to do this" moments. If the key name matches the column name in the table, is there a more simple way to insert all of it?
Code for example:
$statement = $db->prepare("INSERT INTO `applications`(`username`, `email`, `password`, `name`) VALUES (?,?,?,?)");
$statement->execute(array($_POST['username'], $_POST['email'],$_POST['password'],$_POST['name']));
This code WORKS but it just seems a bit over-the-top (especially as more and more columns are added).
I would do it this way:
Declare the columns first. We'll use these to extract a subset of $_POST for use as columns. Otherwise a user could pass bogus request parameters that don't match any columns of the table, which would break our SQL.
$columns = array('username','email','password','name');
$column_list = join(',', $columns);
Create named parameter placeholders i.e. :username.
$param_list = join(',', array_map(function($col) { return ":$col"; }, $columns));
Form the SQL separately, because it's easier to read and debug if it's in its own variable.
$sql = "INSERT INTO `applications` ($column_list) VALUES ($param_list)";
Always check for error status returned from prepare() and execute().
$statement = $db->prepare($sql);
if ($statement === false) {
die(print_r($db->errorInfo(), true));
}
Here we take only the fields of $_POST that match the columns we want to insert.
$param_values = array_intersect_key($_POST, array_flip($columns));
And pass that array to execute(). Again, check for error return status.
$status = $statement->execute($param_values);
if ($status === false) {
die(print_r($statement->errorInfo(), true));
}
I have an array like this
$a = array( 'phone' => 111111111, 'image' => "sadasdasd43eadasdad" );
When I do a var-dump I get this ->
{ ["phone"]=> int(111111111) ["image"]=> string(19) "sadasdasd43eadasdad" }
Now I am trying to add this to the DB using the IN statement -
$q = $DBH->prepare("INSERT INTO user :column_string VALUES :value_string");
$q->bindParam(':column_string',implode(',',array_keys($a)));
$q->bindParam(':value_string',implode(',',array_values($a)));
$q->execute();
The problem I am having is that implode return a string. But the 'phone' column is an integer in the database and also the array is storing it as an integer. Hence I am getting the SQL error as my final query look like this --
INSERT INTO user 'phone,image' values '111111111,sadasdasd43eadasdad';
Which is a wrong query. Is there any way around it.
My column names are dynamic based what the user wants to insert. So I cannot use the placeholders like :phone and :image as I may not always get a values for those two columns. Please let me know if there is a way around this. otherwise I will have to define multiple functions each type of update.
Thanks.
Last time I checked, it was not possible to prepare a statement where the affected columns were unknown at preparation time - but that thing seems to work - maybe your database system is more forgiving than those I am using (mainly postgres)
What is clearly wrong is the implode() statement, as each variable should be handled by it self, you also need parenthesis around the field list in the insert statement.
To insert user defined fields, I think you have to do something like this (at least that how I do it);
$fields=array_keys($a); // here you have to trust your field names!
$values=array_values($a);
$fieldlist=implode(',',$fields);
$qs=str_repeat("?,",count($fields)-1);
$sql="insert into user($fieldlist) values(${qs}?)";
$q=$DBH->prepare($sql);
$q->execute($values);
If you cannot trust the field names in $a, you have to do something like
foreach($a as $f=>$v){
if(validfield($f)){
$fields[]=$f;
$values[]=$v;
}
}
Where validfields is a function that you write that tests each fieldname and checks if it is valid (quick and dirty by making an associative array $valfields=array('name'=>1,'email'=>1, 'phone'=>1 ... and then checking for the value of $valfields[$f], or (as I would prefer) by fetching the field names from the server)
SQL query parameters can be used only where you would otherwise put a literal value.
So if you could see yourself putting a quoted string literal, date literal, or numeric literal in that position in the query, you can use a parameter.
You can't use a parameter for a column name, a table name, a lists of values, an SQL keyword, or any other expressions or syntax.
For those cases, you still have to interpolate content into the SQL string, so you have some risk of SQL injection. The way to protect against that is with whitelisting the column names, and rejecting any input that doesn't match the whitelist.
Because all other answers allow SQL injection. For user input you need to filter for allowed field names:
// change this
$fields = array('email', 'name', 'whatever');
$fieldlist = implode(',', $fields);
$values = array_values(array_intersect_key($_POST, array_flip($fields)));
$qs = str_repeat("?,",count($fields)-1) . '?';
$q = $db->prepare("INSERT INTO events ($fieldlist) values($qs)");
$q->execute($values);
I appreciated MortenSickel's answer, but I wanted to use named parameters to be on the safe side:
$keys = array_keys($a);
$sql = "INSERT INTO user (".implode(", ",$keys).") \n";
$sql .= "VALUES ( :".implode(", :",$keys).")";
$q = $this->dbConnection->prepare($sql);
return $q->execute($a);
You actually can have the :phone and :image fields bound with null values in advance. The structure of the table is fixed anyway and you probably should got that way.
But the answer to your question might look like this:
$keys = ':' . implode(', :', array_keys($array));
$values = str_repeat('?, ', count($array)-1) . '?';
$i = 1;
$q = $DBH->prepare("INSERT INTO user ($keys) VALUES ($values)");
foreach($array as $value)
$q->bindParam($i++, $value, PDO::PARAM_STR, mb_strlen($value));
I know this question has be answered a long time ago, but I found it today and have a little contribution in addition to the answer of #MortenSickel.
The class below will allow you to insert or update an associative array to your database table. For more information about MySQL PDO please visit: http://php.net/manual/en/book.pdo.php
<?php
class dbConnection
{
protected $dbConnection;
function __construct($dbSettings) {
$this->openDatabase($dbSettings);
}
function openDatabase($dbSettings) {
$dsn = 'mysql:host='.$dbSettings['host'].';dbname='.$dbSettings['name'];
$this->dbConnection = new PDO($dsn, $dbSettings['username'], $dbSettings['password']);
$this->dbConnection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
function insertArray($table, $array) {
$fields=array_keys($array);
$values=array_values($array);
$fieldlist=implode(',', $fields);
$qs=str_repeat("?,",count($fields)-1);
$sql="INSERT INTO `".$table."` (".$fieldlist.") VALUES (${qs}?)";
$q = $this->dbConnection->prepare($sql);
return $q->execute($values);
}
function updateArray($table, $id, $array) {
$fields=array_keys($array);
$values=array_values($array);
$fieldlist=implode(',', $fields);
$qs=str_repeat("?,",count($fields)-1);
$firstfield = true;
$sql = "UPDATE `".$table."` SET";
for ($i = 0; $i < count($fields); $i++) {
if(!$firstfield) {
$sql .= ", ";
}
$sql .= " ".$fields[$i]."=?";
$firstfield = false;
}
$sql .= " WHERE `id` =?";
$sth = $this->dbConnection->prepare($sql);
$values[] = $id;
return $sth->execute($values);
}
}
?>
dbConnection class usage:
<?php
$dbSettings['host'] = 'localhost';
$dbSettings['name'] = 'databasename';
$dbSettings['username'] = 'username';
$dbSettings['password'] = 'password';
$dbh = new dbConnection( $dbSettings );
$a = array( 'phone' => 111111111, 'image' => "sadasdasd43eadasdad" );
$dbh->insertArray('user', $a);
// This will asume your table has a 'id' column, id: 1 will be updated in the example below:
$dbh->updateArray('user', 1, $a);
?>
public function insert($data = [] , $table = ''){
$keys = array_keys($data);
$fields = implode(',',$keys);
$pre_fields = ':'.implode(', :',$keys);
$query = parent::prepare("INSERT INTO $table($fields) VALUES($pre_fields) ");
return $query->execute($data);
}
I'm using this code and I'm beyond frustration:
try {
$dbh = new PDO('mysql:dbname=' . DB . ';host=' . HOST, USER, PASS);
$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$dbh->setAttribute(PDO::MYSQL_ATTR_INIT_COMMAND, "SET NAMES 'utf8'");
}
catch(PDOException $e)
{
...
}
$stmt = $dbh->prepare('INSERT INTO table(v1, v2, ...) VALUES(:v1, :v2, ...)');
$stmt->bindParam(':v1', PDO::PARAM_NULL); // --> Here's the problem
PDO::PARAM_NULL, null, '', all of them fail and throw this error:
Fatal error: Cannot pass parameter 2 by reference in /opt/...
You need to use bindValue, not bindParam
bindParam takes a variable by reference, and doesn't pull in a value at the time of calling bindParam. I found this in a comment on the PHP docs:
bindValue(':param', null, PDO::PARAM_INT);
P.S. You may be tempted to do this bindValue(':param', null, PDO::PARAM_NULL); but it did not work for everybody (thank you Will Shaver for reporting.)
When using bindParam() you must pass in a variable, not a constant. So before that line you need to create a variable and set it to null
$myNull = null;
$stmt->bindParam(':v1', $myNull, PDO::PARAM_NULL);
You would get the same error message if you tried:
$stmt->bindParam(':v1', 5, PDO::PARAM_NULL);
When using INTEGER columns (that can be NULL) in MySQL, PDO has some (to me) unexpected behaviour.
If you use $stmt->execute(Array), you have to specify the literal NULL and cannot give NULL by variable reference.
So this won't work:
// $val is sometimes null, but sometimes an integer
$stmt->execute(array(
':param' => $val
));
// will cause the error 'incorrect integer value' when $val == null
But this will work:
// $val again is sometimes null, but sometimes an integer
$stmt->execute(array(
':param' => isset($val) ? $val : null
));
// no errors, inserts NULL when $val == null, inserts the integer otherwise
Tried this on MySQL 5.5.15 with PHP 5.4.1
For those who still have problems (Cannot pass parameter 2 by reference), define a variable with null value, not just pass null to PDO:
bindValue(':param', $n = null, PDO::PARAM_INT);
Hope this helps.
I had the same problem and I found this solution working with bindParam :
bindParam(':param', $myvar = NULL, PDO::PARAM_INT);
If you want to insert NULL only when the value is empty or '', but insert the value when it is available.
A) Receives the form data using POST method, and calls function insert with those values.
insert( $_POST['productId'], // Will be set to NULL if empty
$_POST['productName'] ); // Will be to NULL if empty
B) Evaluates if a field was not filled up by the user, and inserts NULL if that's the case.
public function insert( $productId, $productName )
{
$sql = "INSERT INTO products ( productId, productName )
VALUES ( :productId, :productName )";
//IMPORTANT: Repace $db with your PDO instance
$query = $db->prepare($sql);
//Works with INT, FLOAT, ETC.
$query->bindValue(':productId', !empty($productId) ? $productId : NULL, PDO::PARAM_INT);
//Works with strings.
$query->bindValue(':productName',!empty($productName) ? $productName : NULL, PDO::PARAM_STR);
$query->execute();
}
For instance, if the user doesn't input anything on the productName field of the form, then $productName will be SET but EMPTY. So, you need check if it is empty(), and if it is, then insert NULL.
Tested on PHP 5.5.17
Good luck,
Several answers have given examples of what you should do. But they haven't really explained why you should do one of those things.
The bindParam method is meant to be used with something like a loop (or just repeated statements). It binds a variable reference. So something like
$stmt = $dbh->prepare('INSERT INTO t1 (v1) VALUES(:v1)');
$stmt->bindParam(':v1', $i, PDO::PARAM_INT);
for ($i = 0; $i < 10; $i++) {
$stmt->execute();
}
Would insert values 0 through 9 in a table.
That's obviously a very simple example that could be implemented in other, more efficient ways. You could have more complex logic here. But the basic idea is that you bind a reference to a variable and then you can change the value of the variable.
You can get around the need for a reference by creating a variable before calling bindParam. But in your case, you don't particularly want to bind to a variable reference. You just want to bind a value. So go ahead and do exactly that with bindValue.
You can mostly just use bindValue. But to show why both methods exist, let's rewrite the previous example to use bindValue instead of bindParam:
$stmt = $dbh->prepare('INSERT INTO t1 (v1) VALUES(:v1)');
for ($i = 0; $i < 10; $i++) {
$stmt->bindValue(':v1', $i, PDO::PARAM_INT);
$stmt->execute();
}
This will work, but you have to call bindValue on every iteration of the loop whereas you only needed to call bindParam once. But you aren't doing anything like that, so you can just
$stmt->bindValue(':v1', null, PDO::PARAM_INT);
And everything will work, as stated in the accepted answer. Because you want to bind a value, not a variable reference.
Based on the other answers but with a little more clarity on how to actually use this solution.
If for example you have an empty string for a time value but you want to save it as a null:
if($endtime == ""){
$db->bind(":endtime",$endtime=NULL,PDO::PARAM_STR);
}else{
$db->bind("endtime",$endtime);
}
Notice that for time values you would use PARAM_STR, as times are stored as strings.
So you just need to add an extra If statement that properly changes your variable to NULL before you call bindParam(). Here is an example that I figured out for my situation (I was stuck on this for days trying to INSERT a new DB record with a NULL value for one column):
if ($this->companyid == 'NULL' || $this->companyid == NULL) {
$this->companyid = NULL;
$this->companyname = NULL;
$stmt->bindParam(':companyid', $this->companyid);
$stmt->bindParam(':companyname', $this->companyname);
} else {
$stmt->bindParam(':companyid', $this->companyid);
$stmt->bindParam(':companyname', $this->companyname);
}
Try This.
$stmt->bindValue(':v1', null, PDO::PARAM_NULL); // --> insert null
In my case I am using:
SQLite,
prepared statements with placeholders to handle unknown number of fields,
AJAX request sent by user where everything is a string and there is no such thing like NULL value and
I desperately need to insert NULLs as that does not violates foreign key constrains (acceptable value).
Suppose, now user sends with post: $_POST[field1] with value value1 which can be the empty string "" or "null" or "NULL".
First I make the statement:
$stmt = $this->dbh->prepare("INSERT INTO $table ({$sColumns}) VALUES ({$sValues})");
where {$sColumns} is sth like field1, field2, ... and {$sValues} are my placeholders ?, ?, ....
Then, I collect my $_POST data related with the column names in an array $values and replace with NULLs:
for($i = 0; $i < \count($values); $i++)
if((\strtolower($values[$i]) == 'null') || ($values[$i] == ''))
$values[$i] = null;
Now, I can execute:
$stmt->execute($values);
and among other bypass foreign key constrains.
If on the other hand, an empty string does makes more sense then you have to check if that field is part of a foreign key or not (more complicated).