PHP errors should be turned off on a live site, but occassionally it is useful for debugging purposes to display any error messages.  Depending on the type of hosting, you can generally use one of the following methods:

1. Edit the site’s php.ini file
   

   error_reporting  =  E_ALL
   display_errors = On

   E_ALL = All errors and warnings, as supported, except of level E_STRICT in PHP < 6.

2. Alternatively, you can use an .htaccess file
   

   php_flag display_startup_errors on
   php_flag display_errors on
   php_flag html_errors on

Make sure to turn the “On” values to “Off” once you are done to prevent any visitors from seeing the errors.