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# XLI. Filter Functions

# Introduction

This extension serves for validating and filtering data coming usually from some insecure source such as user input.

Warning
This extension is EXPERIMENTAL. The behaviour of this extension -- including the names of its functions and anything else documented about this extension -- may change without notice in a future release of PHP. Use this extension at your own risk.

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

Table 1. 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" |  |  | Returns `TRUE` for "1", "true", "on" and "yes", `FALSE` for "0", "false", "off", "no", and "", `NULL` otherwise.
`FILTER_VALIDATE_FLOAT` | "float" |  |  | 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_SCHEME_REQUIRED`, `FILTER_FLAG_HOST_REQUIRED`, `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 and +-.
`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.

# Requirements

No external libraries are needed to build this extension.

# Installation

A short installation note: just type

    $ pear install filter

in your console.

# Runtime Configuration

The behaviour of these functions is affected by settings in `php.ini`.

Table 2. Filter Configuration Options

Name | Default | Changeable | Changelog
--- | --- | --- | ---
filter.default | unsafe_raw | PHP_INI_PERDIR |
filter.default_flags |  | PHP_INI_PERDIR |

For further details and definitions of the PHP_INI_* constants, see the Appendix G.

Here's a short explanation of the configuration directives.

filter.default string

  Filter all $_GET, $_POST, $_COOKIE and $_REQUEST data by this filter. Original data can be accessed through input_get().

filter.default_flags integer

  Default flags for filter_data().

# Resource Types

This extension has no resource types defined.

# 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.

`INPUT_DATA` (integer)

  User-defined set of variables.

`FILTER_FLAG_NONE` (integer)

  No flags.

`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_DEFAULT` (integer)

  ID of default ("string") filter.

`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_SCALAR` (integer)

  Allow scalar types (non-array) only in filter. Currently used by input_get_args().

`FILTER_FLAG_ARRAY` (integer)

  Only allow array type in filter. Currently used by input_get_args().

`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_SCHEME_REQUIRED` (integer)

  Require scheme in "validate_url" filter.

`FILTER_FLAG_HOST_REQUIRED` (integer)

  Require host in "validate_url" 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.

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