Call Ajax URL in Plugin

Put below code in _construct() function and change action name to get_product_serial_callback :-

add_action( 'wp_ajax_get_product_serial_callback', array($this,'get_product_serial_callback') );
add_action( 'wp_ajax_nopriv_get_product_serial_callback', array($this,'get_product_serial_callback' ));

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)