PHP 5 Filter Functions

PHP Filter Introduction

This PHP filters is used to validate and filter data coming from insecure sources, like user input.

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Installation

As of PHP 5.2.0, the filter functions are enabled by default. There is no installation needed to use these functions.

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Runtime Configurations

The behavior of these functions is affected by settings in php.ini:

Name	Description	Default	Changeable
filter.default	Filter all $_GET, $_POST, $_COOKIE, $_REQUEST and $_SERVER data by this filter. Accepts the name of the filter you like to use by default. See the filter list for the list of the filter names	"unsafe_raw"	PHP_INI_PERDIR
filter.default_flags	Default flags to apply when the default filter is set. This is set to FILTER_FLAG_NO_ENCODE_QUOTES by default for backwards compatibility reasons	NULL	PHP_INI_PERDIR

PHP 5 Filter Functions

Function	Description
filter_has_var()	Checks if a variable of a specified input type exist
filter_id()	Returns the filter ID of a specified filter name
filter_input()	Gets an external variable (e.g. from form input) and optionally filters it
filter_input_array()	Gets external variables (e.g. from form input) and optionally filters them
filter_list()	Returns a list of all supported filters
filter_var_array()	Gets multiple variables and filter them
filter_var()	Filters a variable with a specified filter

PHP 5 Predefined Filter Constants

Constant	ID	Description
FILTER_VALIDATE_BOOLEAN	258	Validates a boolean
FILTER_VALIDATE_EMAIL	274	Validates an e-mail address
FILTER_VALIDATE_FLOAT	259	Validates a float
FILTER_VALIDATE_INT	257	Validates an integer
FILTER_VALIDATE_IP	275	Validates an IP address
FILTER_VALIDATE_REGEXP	272	Validates a regular expression
FILTER_VALIDATE_URL	273	Validates a URL
FILTER_SANITIZE_EMAIL	517	Removes all illegal characters from an e-mail address
FILTER_SANITIZE_ENCODED	514	Removes/Encodes special characters
FILTER_SANITIZE_MAGIC_QUOTES	521	Apply addslashes()
FILTER_SANITIZE_NUMBER_FLOAT	520	Remove all characters, except digits, +- and optionally .,eE
FILTER_SANITIZE_NUMBER_INT	519	Removes all characters except digits and + -
FILTER_SANITIZE_SPECIAL_CHARS	515	Removes special characters
FILTER_SANITIZE_FULL_SPECIAL_CHARS
FILTER_SANITIZE_STRING	513	Removes tags/special characters from a string
FILTER_SANITIZE_STRIPPED	513	Alias of FILTER_SANITIZE_STRING
FILTER_SANITIZE_URL	518	Removes all illegal character from s URL
FILTER_UNSAFE_RAW	516	Do nothing, optionally strip/encode special characters
FILTER_CALLBACK	1024	Call a user-defined function to filter data

Credit: www.w3schools.com