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.
INPUT_POST
     (integer)
   INPUT_GET
     (integer)
   INPUT_ENV
     (integer)
   INPUT_SERVER
     (integer)
   INPUT_SESSION
     (integer)
   INPUT_REQUEST
     (integer)
   FILTER_FLAG_NONE
     (integer)
   FILTER_REQUIRE_SCALAR
     (integer)
   FILTER_REQUIRE_ARRAY
     (integer)
   FILTER_FORCE_ARRAY
     (integer)
   FILTER_NULL_ON_FAILURE
     (integer)
   FILTER_VALIDATE_INT
     (integer)
   FILTER_VALIDATE_BOOLEAN
     (integer)
   FILTER_VALIDATE_FLOAT
     (integer)
   FILTER_VALIDATE_REGEXP
     (integer)
   FILTER_VALIDATE_URL
     (integer)
   FILTER_VALIDATE_EMAIL
     (integer)
   FILTER_VALIDATE_IP
     (integer)
   FILTER_VALIDATE_MAC
     (integer)
   FILTER_DEFAULT
     (integer)
   FILTER_UNSAFE_RAW.
    
   FILTER_UNSAFE_RAW
     (integer)
   FILTER_SANITIZE_STRING
     (integer)
   FILTER_SANITIZE_STRIPPED
     (integer)
   FILTER_SANITIZE_ENCODED
     (integer)
   FILTER_SANITIZE_SPECIAL_CHARS
     (integer)
   FILTER_SANITIZE_EMAIL
     (integer)
   FILTER_SANITIZE_URL
     (integer)
   FILTER_SANITIZE_NUMBER_INT
     (integer)
   FILTER_SANITIZE_NUMBER_FLOAT
     (integer)
   FILTER_SANITIZE_MAGIC_QUOTES
     (integer)
   FILTER_CALLBACK
     (integer)
   FILTER_FLAG_ALLOW_OCTAL
     (integer)
   FILTER_FLAG_ALLOW_HEX
     (integer)
   FILTER_FLAG_STRIP_LOW
     (integer)
   FILTER_FLAG_STRIP_HIGH
     (integer)
   FILTER_FLAG_ENCODE_LOW
     (integer)
   FILTER_FLAG_ENCODE_HIGH
     (integer)
   FILTER_FLAG_ENCODE_AMP
     (integer)
   FILTER_FLAG_NO_ENCODE_QUOTES
     (integer)
   FILTER_FLAG_EMPTY_STRING_NULL
     (integer)
   FILTER_FLAG_ALLOW_FRACTION
     (integer)
   FILTER_FLAG_ALLOW_THOUSAND
     (integer)
   FILTER_FLAG_ALLOW_SCIENTIFIC
     (integer)
   FILTER_FLAG_PATH_REQUIRED
     (integer)
   FILTER_FLAG_QUERY_REQUIRED
     (integer)
   FILTER_FLAG_IPV4
     (integer)
   FILTER_FLAG_IPV6
     (integer)
   FILTER_FLAG_NO_RES_RANGE
     (integer)
   FILTER_FLAG_NO_PRIV_RANGE
     (integer)