Filter
Installing/Configuring
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
Installing/Configuring
Filter
PHP Manual