PHP 8.0: FILTER_FLAG_SCHEME_REQUIRED and FILTER_FLAG_HOST_REQUIRED flags are removed

Version8.0
TypeRemoval

filter_var() function used to accept two flags that were deprecated in PHP 7.3:

  • FILTER_FLAG_SCHEME_REQUIRED
  • FILTER_FLAG_HOST_REQUIRED

filter_var() function, when used with FILTER_VALIDATE_URL already assumed these two flags, and it was not necessary to use these flags explicitly.

Deprecated in PHP 7.3, these two flags are now removed in PHP 8.0. 

  $var = 'https://php.watch';
- filter_var($var, FILTER_VALIDATE_URL, FILTER_FLAG_SCHEME_REQUIRED);
- filter_var($var, FILTER_VALIDATE_URL, FILTER_FLAG_HOST_REQUIRED);
- filter_var($var, FILTER_VALIDATE_URL, FILTER_FLAG_HOST_REQUIRED | FILTER_FLAG_HOST_REQUIRED);
+ filter_var($var, FILTER_VALIDATE_URL);

If attempted to use these two flags, a fatal error will be thrown:

Fatal error: Uncaught Error: Undefined constant 'FILTER_FLAG_SCHEME_REQUIRED' in ...:...
Fatal error: Uncaught Error: Undefined constant 'FILTER_FLAG_HOST_REQUIRED' in ...:...

Backwards Compatibility Impact

Because the FILTER_FLAG_HOST_REQUIRED and FILTER_FLAG_SCHEME_REQUIRED constants are removed in PHP 8, attempting to use them will now throw a fatal error.

The easiest fix is to simply remove these two flags. filter_var() function when used with FILTER_VALIDATE_URL will always enforce the host-required and scheme-required condions regardless of the presence of these two flags.