SELECT * FROM in MySQLi - php

Question

My site is rather extensive, and I just recently made the switch to PHP5 (call me a late bloomer).
All of my MySQL query's before were built as such:
"SELECT * FROM tablename WHERE field1 = 'value' && field2 = 'value2'";
This made it very easy, simple and friendly.
I am now trying to make the switch to mysqli for obvious security reasons, and I am having a hard time figuring out how to implement the same SELECT * FROM queries when the bind_param requires specific arguments.
Is this statement a thing of the past?
If it is, how do I handle a query with tons of columns involved? Do I really need to type them all out every time?

Answer 1

I could be wrong, but for your question I get the feeling that bind_param() isn't really the problem here. You always need to define some conditions, be it directly in the query string itself, of using bind_param() to set the ? placeholders. That's not really an issue.
The problem I had using MySQLi SELECT * queries is the bind_result() part. That's where it gets interesting. I came across this post from Jeffrey Way: http://jeff-way.com/2009/05/27/tricky-prepared-statements/(This link is no longer active). The script basically loops through the results and returns them as an array — no need to know how many columns there are, and you can still use prepared statements.
In this case it would look something like this:
$stmt = $mysqli->prepare(
'SELECT * FROM tablename WHERE field1 = ? AND field2 = ?');
$stmt->bind_param('ss', $value, $value2);
$stmt->execute();
Then use the snippet from the site:
$meta = $stmt->result_metadata();
while ($field = $meta->fetch_field()) {
$parameters[] = &$row[$field->name];
}
call_user_func_array(array($stmt, 'bind_result'), $parameters);
while ($stmt->fetch()) {
foreach($row as $key => $val) {
$x[$key] = $val;
}
$results[] = $x;
}
And $results now contains all the info from SELECT *. So far I found this to be an ideal solution.

Answer 2

"SELECT * FROM tablename WHERE field1 = 'value' && field2 = 'value2'";
becomes
"SELECT * FROM tablename WHERE field1 = ? && field2 = ?";
which is passed to the $mysqli::prepare:
$stmt = $mysqli->prepare(
"SELECT * FROM tablename WHERE field1 = ? && field2 = ?");
$stmt->bind_param( "ss", $value, $value2);
// "ss' is a format string, each "s" means string
$stmt->execute();
$stmt->bind_result($col1, $col2);
// then fetch and close the statement
OP comments:
so if i have 5 parameters, i could potentially have "sssis" or something (depending on the types of inputs?)
Right, one type specifier per ? parameter in the prepared statement, all of them positional (first specifier applies to first ? which is replaced by first actual parameter (which is the second parameter to bind_param)).

Answer 3

While you are switching, switch to PDO instead of mysqli, It helps you write database agnositc code and have better features for prepared statements.
http://www.php.net/pdo
Bindparam for PDO:
http://se.php.net/manual/en/pdostatement.bindparam.php
$sth = $dbh->prepare("SELECT * FROM tablename WHERE field1 = :value1 && field2 = :value2");
$sth->bindParam(':value1', 'foo');
$sth->bindParam(':value2', 'bar');
$sth->execute();
or:
$sth = $dbh->prepare("SELECT * FROM tablename WHERE field1 = ? && field2 = ?");
$sth->bindParam(1, 'foo');
$sth->bindParam(2, 'bar');
$sth->execute();
or execute with the parameters as an array:
$sth = $dbh->prepare("SELECT * FROM tablename WHERE field1 = :value1 && field2 = :value2");
$sth->execute(array(':value1' => 'foo' , ':value2' => 'bar'));
It will be easier for you if you would like your application to be able to run on different databases in the future.
I also think you should invest some time in using some of the classes from Zend Framwework whilst working with PDO. Check out their Zend_Db and more specifically [Zend_Db_Factory][2]. You do not have to use all of the framework or convert your application to the MVC pattern, but using the framework and reading up on it is time well spent.

Answer 4

Is this statement a thing of the past?
Yes. Don't use SELECT *; it's a maintenance nightmare. There are tons of other threads on SO about why this construct is bad, and how avoiding it will help you write better queries.
See also:
What is the reason not to use select *?
Performance issue in using SELECT *?
Why is using '*' to build a view bad?

Answer 5

You can still use it (mysqli is just another way of communicating with the server, the SQL language itself is expanded, not changed). Prepared statements are safer, though - since you don't need to go through the trouble of properly escaping your values each time. You can leave them as they were, if you want to but the risk of sql piggybacking is reduced if you switch.

Answer 6

you can use get_result() on the statement.
http://php.net/manual/en/mysqli-stmt.get-result.php

Answer 7

I was looking for a nice and complete example of how to bind multiple query parameters dynamically to any SELECT, INSERT, UPDATE and DELETE query. Alec mentions in his answer a way of how to bind result, for me the get_result() after execute() function for SELECT queries works just fine, and am able to retrieve all the selected results into an array of associative arrays.
Anyway, I ended up creating a function where I am able to dynamically bind any amount of parameters to a parametrized query ( using call_user_func_array function) and obtain a result of the query execution. Below is the function with its documentation (please read before it before using - especially the $paremetersTypes - Type specification chars parameter is important to understand)
/**
* Prepares and executes a parametrized QUERY (SELECT, INSERT, UPDATE, DELETE)
*
* #param[in] $dbConnection mysqli database connection to be used for query execution
* #param[in] $dbQuery parametrized query to be bind parameters for and then execute
* #param[in] $isDMQ boolean value, should be set to TRUE for (DELETE, INSERT, UPDATE - Data manipulaiton queries), FALSE for SELECT queries
* #param[in] $paremetersTypes String representation for input parametrs' types as per http://php.net/manual/en/mysqli-stmt.bind-param.php
* #param[in] $errorOut A variable to be passed by reference where a string representation of an error will be present if a FAUILURE occurs
* #param[in] $arrayOfParemetersToBind Parameters to be bind to the parametrized query, parameters need to be specified in an array in the correct order
* #return array of feched records associative arrays for SELECT query on SUCCESS, TRUE for INSERT, UPDATE, DELETE queries on SUCCESS, on FAIL sets the error and returns NULL
*/
function ExecuteMySQLParametrizedQuery($dbConnection, $dbQuery, $isDMQ, $paremetersTypes, &$errorOut, $arrayOfParemetersToBind)
{
$stmt = $dbConnection->prepare($dbQuery);
$outValue = NULL;
if ($stmt === FALSE)
$errorOut = 'Failed to prepare statement for query: ' . $dbQuery;
else if ( call_user_func_array(array($stmt, "bind_param"), array_merge(array($paremetersTypes), $arrayOfParemetersToBind)) === FALSE)
$errorOut = 'Failed to bind required parameters to query: ' . $dbQuery . ' , parameters :' . json_encode($arrayOfParemetersToBind);
else if (!$stmt->execute())
$errorOut = "Failed to execute query [$dbQuery] , erorr:" . $stmt->error;
else
{
if ($isDMQ)
$outValue = TRUE;
else
{
$result = $stmt->get_result();
if ($result === FALSE)
$errorOut = 'Failed to obtain result from statement for query ' . $dbQuery;
else
$outValue = $result->fetch_all(MYSQLI_ASSOC);
}
}
$stmt->close();
return $outValue;
}
usage:
$param1 = "128989";
$param2 = "some passcode";
$insertQuery = "INSERT INTO Cards (Serial, UserPin) VALUES (?, ?)";
$rowsInserted = ExecuteMySQLParametrizedQuery($dbConnection, $insertQuery, TRUE, 'ss', $errorOut, array(&$param1, &$param2) ); // Make sure the parameters in an array are passed by reference
if ($rowsInserted === NULL)
echo 'error ' . $errorOut;
else
echo "successfully inserted row";
$selectQuery = "SELECT CardID FROM Cards WHERE Serial like ? AND UserPin like ?";
$arrayOfCardIDs = ExecuteMySQLParametrizedQuery($dbConnection, $selectQuery, FALSE, 'ss', $errorOut, array(&$param1, &$param2) ); // Make sure the parameters in an array are passed by reference
if ($arrayOfCardIDs === NULL)
echo 'error ' . $errorOut;
else
{
echo 'obtained result array of ' . count($arrayOfCardIDs) . 'selected rows';
if (count($arrayOfCardIDs) > 0)
echo 'obtained card id = ' . $arrayOfCardIDs[0]['CardID'];
}