ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);
error_reporting(E_ALL);
//OR
ini_set('display_errors', 1);
ini_set('display_startup_errors', 0);
error_reporting(E_ALL & ~E_NOTICE);

<?php
error_reporting(E_ALL);
ini_set('display_errors', 'On');

; This directive controls whether or not and where PHP will output errors,
; notices and warnings too. Error output is very useful during development, but
; it could be very dangerous in production environments. Depending on the code
; which is triggering the error, sensitive information could potentially leak
; out of your application such as database usernames and passwords or worse.
; For production environments, we recommend logging errors rather than
; sending them to STDOUT.
; Possible Values:
; Off = Do not display any errors
; stderr = Display errors to STDERR (affects only CGI/CLI binaries!)
; On or stdout = Display errors to STDOUT
; Default Value: On
; Development Value: On
; Production Value: Off
; http://php.net/display-errors
display_errors = On