PHP Fatal error: Call to undefined function mysql_connect
This error generated due to mysql module not configured in your php . To verify this can use the function get_loaded_extensions(); . So, Create a file with name of exetension.php add below code and execute.
It will shows you list of loaded modules, If you could not found the line number  => mysql or  => mysqli better you can trying to uninstall existing php & mysql and install yum install php mysql.