Handling Prepared Statements with IN() Condition in WordPress

WordPress provides prepared statements to protect against SQL injection attacks and improve query performance. However, using the IN() condition with multiple values in a string can present challenges.

Problem Statement:

Consider the following situation:

$villes = '"paris","fes","rabat"';
$sql = 'SELECT distinct telecopie FROM `comptage_fax` WHERE `ville` IN(%s)';
$query = $wpdb->prepare($sql, $villes);

This code does not properly escape the string, resulting in a single string with escaped double quotes:

SELECT distinct telecopie FROM `comptage_fax` WHERE `ville` IN('\"paris\",\"fes\",\"rabat\"')

Solution:

To correctly implement a prepared statement with multiple values in WordPress, follow these steps:

// Create an array of the values to use in the list
$villes = array('paris', 'fes', 'rabat');

// Generate the SQL statement.
// Number of %s items based on length of $villes array
$sql = "
  SELECT DISTINCT telecopie
  FROM `comptage_fax`
  WHERE `ville` IN(" . implode(', ', array_fill(0, count($villes), '%s')) . ")
";

// Call $wpdb->prepare passing the values of the array as separate arguments
$query = call_user_func_array(array($wpdb, 'prepare'), array_merge(array($sql), $villes));

PHP Functions Used:

• implode() - Joins array elements into a string
• array_fill() - Creates an array filled with a specific value
• call_user_func_array() - Calls a function with the parameters passed as an array
• array_merge() - Merges two arrays

This approach ensures that the values in $villes are properly escaped and treated as separate values in the IN() condition.