The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.

FILTER_FLAG_STRIP_LOW (int)

Strip characters with ASCII value less than 32.

FILTER_FLAG_STRIP_HIGH (int)

Strip characters with ASCII value greater than 127.

FILTER_FLAG_STRIP_BACKTICK (int)

Strips backtick (`) characters.

FILTER_FLAG_ENCODE_LOW (int)

Encode characters with ASCII value less than 32.

FILTER_FLAG_ENCODE_HIGH (int)

Encode characters with ASCII value greater than 127.

FILTER_FLAG_ENCODE_AMP (int)

Encode &.

FILTER_FLAG_NO_ENCODE_QUOTES (int)

Single and double quotes (' and ") will not be encoded.

FILTER_FLAG_EMPTY_STRING_NULL (int)

If sanitizing a string results in an empty string, convert the value to null