MySQL extension was deprecated in PHP 5.5.0, and it was removed in PHP 7.0.0 version. For a large and old application, this is difficult to search and replace each function.
We can use MySQL functions by creating a wrapper function for each below is running code.
mysql_connect("localhost","user","password"); mysql_select_db("database"); function mysql_connect($host,$user,$pass){ } function mysql_select_db($db){ /* use global so that we can use this connection in other mysql functions */ global $dbconn; $dbconn = new mysqli(_HOST_NAME, _DATABASE_USER_NAME, _DATABASE_PASSWORD, _DATABASE_NAME); if ($dbconn->connect_error) { // trigger your error message } } function mysql_query($query){ global $dbconn; $mysqli_row = mysqli_query($dbconn, $query); return $mysqli_row; } function mysql_insert_id(){ global $dbconn; return mysqli_insert_id($dbconn); } function mysql_fetch_array($result){ $row = mysqli_fetch_array($result, MYSQLI_BOTH); /* MYSQLI_BOTH will return both associative and numeric array */ return $row; } function mysql_num_rows($result){ $row_cnt = mysqli_num_rows($result); return $row_cnt; } function mysql_real_escape_string($val){ global $dbconn; $rl = mysqli_real_escape_string($dbconn, $val); return $rl; }