When you update your WordPress site under PHP 7, the following errors may appear :
Fatal error: Uncaught Error: Call to undefined function mysql_connect() in ...wp-includes/wp-db.php:1665
Stack trace: #0 ...wp-includes/wp-db.php(632): wpdb->db_connect() #1 ...wp-includes/load.php(425)
Fatal error: Uncaught Error: Call to undefined function wp_kses_normalize_entities() in .../wp-includes/formatting.php:4316
Stack trace: #0 .../wp-includes/class-wp-fatal-error-handler.php(190)
Where does this error come from?
By upgrading to PHP 7.3 (or rather from PHP 7.0.0 onwards), the mysql_connect extension has been removed. It was already deprecated since PHP 5.5.0.
Instead, it is recommended to use the mysqli extensions to connect to a database. This extension is more powerful and more secure.
What can be done to solve this problem?
Depending on the origin of the error, there are several solutions:
- Contact your web host and ask if mysqli extensions are enabled.
- Check that you have mysqi enabled on your hosting:
$var_mysqli = function_exists('mysqli_connect'); var_dump($var_mysqli);
- Test your connection with mysqli :
$mysqli_connection = new MySQLi('nom_d_hôte', 'nom_utilisateur', 'mot_de_passe', 'nom_de_la_base_de_données');
- Check your wp-config.php file and verify that the following variable :
is set to “false”.