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 Predefined Constants
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)
    
     POST variables.
    
   
    INPUT_GET(integer)
    
     GET variables.
    
   
    INPUT_COOKIE(integer)
    
     COOKIE variables.
    
   
    INPUT_ENV(integer)
    
     ENV variables.
    
   
    INPUT_SERVER(integer)
    
     SERVER variables.
    
   
    INPUT_SESSION(integer)
    
     SESSION variables.
    (not implemented yet)
    
   
    INPUT_REQUEST(integer)
    
     REQUEST variables.
    (not implemented yet)
    
   
    FILTER_FLAG_NONE(integer)
    
     No flags.
    
   
    FILTER_REQUIRE_SCALAR(integer)
    
      Flag used to require scalar as input
    
   
    FILTER_REQUIRE_ARRAY(integer)
    
      Require an array as input. 
    
   
    FILTER_FORCE_ARRAY(integer)
    
     Always returns an array.
    
   
    FILTER_NULL_ON_FAILURE(integer)
    
     Use NULL instead of FALSE on failure. 
    
   
    FILTER_VALIDATE_INT(integer)
    
     ID of "int" filter.
    
   
    FILTER_VALIDATE_BOOLEAN(integer)
    
     ID of "boolean" filter.
    
   
    FILTER_VALIDATE_FLOAT(integer)
    
     ID of "float" filter.
    
   
    FILTER_VALIDATE_REGEXP(integer)
    
     ID of "validate_regexp" filter.
    
   
    FILTER_VALIDATE_URL(integer)
    
     ID of "validate_url" filter.
    
   
    FILTER_VALIDATE_EMAIL(integer)
    
     ID of "validate_email" filter.
    
   
    FILTER_VALIDATE_IP(integer)
    
     ID of "validate_ip" filter.
    
   
    FILTER_VALIDATE_MAC(integer)
    
     ID of "validate_mac_address" filter.
     (Available as of PHP 5.5.0)
    
   
    FILTER_DEFAULT(integer)
    
    ID of default ("unsafe_raw") filter. This is equivalent to
    FILTER_UNSAFE_RAW.
    FILTER_UNSAFE_RAW(integer)
    
     ID of "unsafe_raw" filter.
    
   
    FILTER_SANITIZE_STRING(integer)
    
     ID of "string" filter.
    
   
    FILTER_SANITIZE_STRIPPED(integer)
    
     ID of "stripped" filter.
    
   
    FILTER_SANITIZE_ENCODED(integer)
    
     ID of "encoded" filter.
    
   
    FILTER_SANITIZE_SPECIAL_CHARS(integer)
    
     ID of "special_chars" filter.
    
   
    FILTER_SANITIZE_EMAIL(integer)
    
     ID of "email" filter.
    
   
    FILTER_SANITIZE_URL(integer)
    
     ID of "url" filter.
    
   
    FILTER_SANITIZE_NUMBER_INT(integer)
    
     ID of "number_int" filter.
    
   
    FILTER_SANITIZE_NUMBER_FLOAT(integer)
    
     ID of "number_float" filter.
    
   
    FILTER_SANITIZE_MAGIC_QUOTES(integer)
    
     ID of "magic_quotes" filter.
    
   
    FILTER_CALLBACK(integer)
    
     ID of "callback" filter.
    
   
    FILTER_FLAG_ALLOW_OCTAL(integer)
    
     Allow octal notation (0[0-7]+) in "int" filter.
    
   
    FILTER_FLAG_ALLOW_HEX(integer)
    
     Allow hex notation (0x[0-9a-fA-F]+) in "int" filter.
    
   
    FILTER_FLAG_STRIP_LOW(integer)
    
     Strip characters with ASCII value less than 32.
    
   
    FILTER_FLAG_STRIP_HIGH(integer)
    
     Strip characters with ASCII value greater than 127.
    
   
    FILTER_FLAG_ENCODE_LOW(integer)
    
     Encode characters with ASCII value less than 32.
    
   
    FILTER_FLAG_ENCODE_HIGH(integer)
    
     Encode characters with ASCII value greater than 127.
    
   
    FILTER_FLAG_ENCODE_AMP(integer)
    
     Encode &.
    
   
    FILTER_FLAG_NO_ENCODE_QUOTES(integer)
    
     Don't encode ' and ".
    
   
    FILTER_FLAG_EMPTY_STRING_NULL(integer)
    
     (No use for now.)
    
   
    FILTER_FLAG_ALLOW_FRACTION(integer)
    
     Allow fractional part in "number_float" filter.
    
   
    FILTER_FLAG_ALLOW_THOUSAND(integer)
    
     Allow thousand separator (,) in "number_float" filter.
    
   
    FILTER_FLAG_ALLOW_SCIENTIFIC(integer)
    
     Allow scientific notation (e, E) in
     "number_float" filter.
    
   
    FILTER_FLAG_PATH_REQUIRED(integer)
    
     Require path in "validate_url" filter.
    
   
    FILTER_FLAG_QUERY_REQUIRED(integer)
    
     Require query in "validate_url" filter.
    
   
    FILTER_FLAG_IPV4(integer)
    
     Allow only IPv4 address in "validate_ip" filter.
    
   
    FILTER_FLAG_IPV6(integer)
    
     Allow only IPv6 address in "validate_ip" filter.
    
   
    FILTER_FLAG_NO_RES_RANGE(integer)
    
     Deny reserved addresses in "validate_ip" filter.
    
   
    FILTER_FLAG_NO_PRIV_RANGE(integer)
    
     Deny private addresses in "validate_ip" filter.
    
   
    FILTER_FLAG_EMAIL_UNICODE(integer)
    
     Accepts Unicode characters in the local part in "validate_email" filter.
     (Available as of PHP 7.1.0)
    
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