| ID | Used with | Description | 
|---|---|---|
| FILTER_FLAG_STRIP_LOW | FILTER_SANITIZE_ENCODED,FILTER_SANITIZE_SPECIAL_CHARS,FILTER_SANITIZE_STRING,FILTER_UNSAFE_RAW | Strips characters that have a numerical value <32. | 
| FILTER_FLAG_STRIP_HIGH | FILTER_SANITIZE_ENCODED,FILTER_SANITIZE_SPECIAL_CHARS,FILTER_SANITIZE_STRING,FILTER_UNSAFE_RAW | Strips characters that have a numerical value >127. | 
| FILTER_FLAG_STRIP_BACKTICK | FILTER_SANITIZE_ENCODED,FILTER_SANITIZE_SPECIAL_CHARS,FILTER_SANITIZE_STRING,FILTER_UNSAFE_RAW | Strips backtick characters. | 
| FILTER_FLAG_ALLOW_FRACTION | FILTER_SANITIZE_NUMBER_FLOAT | Allows a period ( .) as a fractional separator in
        numbers. | 
| FILTER_FLAG_ALLOW_THOUSAND | FILTER_SANITIZE_NUMBER_FLOAT,FILTER_VALIDATE_FLOAT | Allows a comma ( ,) as a thousands separator in
        numbers. | 
| FILTER_FLAG_ALLOW_SCIENTIFIC | FILTER_SANITIZE_NUMBER_FLOAT | Allows an eorEfor scientific
        notation in numbers. | 
| FILTER_FLAG_NO_ENCODE_QUOTES | FILTER_SANITIZE_STRING | If this flag is present, single ( ') and double
        (") quotes will not be encoded. | 
| FILTER_FLAG_ENCODE_LOW | FILTER_SANITIZE_ENCODED,FILTER_SANITIZE_STRING,FILTER_SANITIZE_RAW | Encodes all characters with a numerical value <32. | 
| FILTER_FLAG_ENCODE_HIGH | FILTER_SANITIZE_ENCODED,FILTER_SANITIZE_SPECIAL_CHARS,FILTER_SANITIZE_STRING,FILTER_SANITIZE_RAW | Encodes all characters with a numerical value >127. | 
| FILTER_FLAG_ENCODE_AMP | FILTER_SANITIZE_STRING,FILTER_SANITIZE_RAW | Encodes ampersands ( &). | 
| FILTER_NULL_ON_FAILURE | any FILTER_VALIDATE_* | Returns nullfor unrecognized values. | 
| FILTER_FLAG_ALLOW_OCTAL | FILTER_VALIDATE_INT | Regards inputs starting with a zero ( 0) as octal
        numbers. This only allows the succeeding digits to be0-7. | 
| FILTER_FLAG_ALLOW_HEX | FILTER_VALIDATE_INT | Regards inputs starting with 0xor0Xas hexadecimal numbers. This only allows
        succeeding characters to bea-fA-F0-9. | 
| FILTER_FLAG_EMAIL_UNICODE | FILTER_VALIDATE_EMAIL | Allows the local part of the email address to contain Unicode characters. | 
| FILTER_FLAG_IPV4 | FILTER_VALIDATE_IP | Allows the IP address to be in IPv4 format. | 
| FILTER_FLAG_IPV6 | FILTER_VALIDATE_IP | Allows the IP address to be in IPv6 format. | 
| FILTER_FLAG_NO_PRIV_RANGE | FILTER_VALIDATE_IP | 
         Fails validation for the following private IPv4 ranges:
          
         Fails validation for the IPv6 addresses starting with
          | 
| FILTER_FLAG_NO_RES_RANGE | FILTER_VALIDATE_IP | 
        Fails validation for the following reserved IPv4 ranges:
         
         Fails validation for the following reserved IPv6 ranges:
          These are the ranges that are marked as Reserved-By-Protocol in » RFC 6890. | 
| FILTER_FLAG_SCHEME_REQUIRED | FILTER_VALIDATE_URL | Requires the URL to contain a scheme part. | 
| FILTER_FLAG_HOST_REQUIRED | FILTER_VALIDATE_URL | Requires the URL to contain a host part. | 
| FILTER_FLAG_PATH_REQUIRED | FILTER_VALIDATE_URL | Requires the URL to contain a path part. | 
| FILTER_FLAG_QUERY_REQUIRED | FILTER_VALIDATE_URL | Requires the URL to contain a query string. | 
| FILTER_REQUIRE_SCALAR | Requires the value to be scalar. | |
| FILTER_REQUIRE_ARRAY | Requires the value to be an array. | |
| FILTER_FORCE_ARRAY | If the value is a scalar, it is treated as array with the scalar value as only element. | 
| 版本 | 说明 | 
|---|---|
| 7.3.0 | The explicit usage of FILTER_FLAG_SCHEME_REQUIREDandFILTER_FLAG_HOST_REQUIREDhas been deprecated. | 
| 7.1.0 | FILTER_FLAG_EMAIL_UNICODEhas been added. |