This method works only for websites on PHP 5: the mysql extension was removed in PHP 7.0, so on PHP 7 and later you need to install the mysqli extension instead.
In the /bitrix/php_interface/dbconn.php file, set the constant:
define("BX_USE_MYSQLI", false);
In the /bitrix/.settings.php file, change the database connection class to MysqlConnection:
'connections' =>
array (
'value' =>
array (
'default' =>
array (
'className' => '\\Bitrix\\Main\\DB\\MysqlConnection',













