HOW TO Use Multiple Filter Flags in PHP Filter Functions

Using multiple filter flags in PHP is easy, but the documentation does not explain it well.

The Filter capabilities in PHP 5.3 and above are very powerful and save a ton of effort, but the passing of flags to various filter functions is described minimally as a “bitwise disjunction of flags”. This means you need to pass a bitwise conjunction of flags.

Here’s the english translation:
Pass a pipe-separated list of flags.

That’s it. You need to use the logical ‘OR’ to create a parameter the parser will understand.

If you want to use filter_var() to sanitize $string with FILTER_SANITIZE_STRING and pass in FILTER_FLAG_STRIP_HIGH and FILTER_FLAG_STRIP_LOW, just call it like this:

$string = filter_var($string, FILTER_SANITIZE_STRING, FILTER_FLAG_NO_ENCODE_QUOTES | FILTER_FLAG_STRIP_HIGH | FILTER_FLAG_STRIP_LOW);

That’s it. Nothing magical.

The same goes for passing a flags field in an options array in the case of using callbacks. Here is an extended version of the example from php.net:

$var = filter_var($string, FILTER_SANITIZE_SPECIAL_CHARS,
array('flags' => FILTER_FLAG_STRIP_LOW | FILTER_FLAG_ENCODE_HIGH));

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