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Filter
PHP Manual

Introduction

This extension serves to validate and filter data coming from some insecure source, such as user input.

The following filters currently exist; be sure to read the Filter Constants section for information that describes the behavior of each constant:

Existing filters
ID Name Options Flags Description
FILTER_VALIDATE_INT "int" min_range , max_range FILTER_FLAG_ALLOW_OCTAL, FILTER_FLAG_ALLOW_HEX Validates value as integer, optionally from the specified range.
FILTER_VALIDATE_BOOLEAN "boolean"   FILTER_NULL_ON_FAILURE

Returns TRUE for "1", "true", "on" and "yes". Returns FALSE otherwise.

If FILTER_NULL_ON_FAILURE is set, FALSE is returned only for "0", "false", "off", "no", and "", and NULL is returned for all non-boolean values.

FILTER_VALIDATE_FLOAT "float" decimal FILTER_FLAG_ALLOW_THOUSAND Validates value as float.
FILTER_VALIDATE_REGEXP "validate_regexp" regexp   Validates value against regexp , a Perl-compatible regular expression.
FILTER_VALIDATE_URL "validate_url"   FILTER_FLAG_PATH_REQUIRED, FILTER_FLAG_QUERY_REQUIRED Validates value as URL, optionally with required components.
FILTER_VALIDATE_EMAIL "validate_email"     Validates value as e-mail.
FILTER_VALIDATE_IP "validate_ip"   FILTER_FLAG_IPV4, FILTER_FLAG_IPV6, FILTER_FLAG_NO_PRIV_RANGE, FILTER_FLAG_NO_RES_RANGE Validates value as IP address, optionally only IPv4 or IPv6 or not from private or reserved ranges.
FILTER_SANITIZE_STRING "string"   FILTER_FLAG_NO_ENCODE_QUOTES, FILTER_FLAG_STRIP_LOW, FILTER_FLAG_STRIP_HIGH, FILTER_FLAG_ENCODE_LOW, FILTER_FLAG_ENCODE_HIGH, FILTER_FLAG_ENCODE_AMP Strip tags, optionally strip or encode special characters.
FILTER_SANITIZE_STRIPPED "stripped"     Alias of "string" filter.
FILTER_SANITIZE_ENCODED "encoded"   FILTER_FLAG_STRIP_LOW, FILTER_FLAG_STRIP_HIGH, FILTER_FLAG_ENCODE_LOW, FILTER_FLAG_ENCODE_HIGH URL-encode string, optionally strip or encode special characters.
FILTER_SANITIZE_SPECIAL_CHARS "special_chars"   FILTER_FLAG_STRIP_LOW, FILTER_FLAG_STRIP_HIGH, FILTER_FLAG_ENCODE_HIGH HTML-escape '"<>& and characters with ASCII value less than 32, optionally strip or encode other special characters.
FILTER_UNSAFE_RAW "unsafe_raw"   FILTER_FLAG_STRIP_LOW, FILTER_FLAG_STRIP_HIGH, FILTER_FLAG_ENCODE_LOW, FILTER_FLAG_ENCODE_HIGH, FILTER_FLAG_ENCODE_AMP Do nothing, optionally strip or encode special characters.
FILTER_SANITIZE_EMAIL "email"     Remove all characters except letters, digits and !#$%&'*+-/=?^_`{|}~@.[].
FILTER_SANITIZE_URL "url"     Remove all characters except letters, digits and $-_.+!*'(),{}|\\^~[]`<>#%";/?:@&=.
FILTER_SANITIZE_NUMBER_INT "number_int"     Remove all characters except digits, plus and minus sign.
FILTER_SANITIZE_NUMBER_FLOAT "number_float"   FILTER_FLAG_ALLOW_FRACTION, FILTER_FLAG_ALLOW_THOUSAND, FILTER_FLAG_ALLOW_SCIENTIFIC Remove all characters except digits, +- and optionally .,eE.
FILTER_SANITIZE_MAGIC_QUOTES "magic_quotes"     Apply addslashes().
FILTER_CALLBACK "callback" callback function or method   Call user-defined function to filter data.


Filter
PHP Manual