# Standard Filter Classes

Zend Framework comes with a standard set of filters, which are ready for you to use.

## Alnum

Returns the string `$value`, removing all but alphabetic and digit characters. This filter includes an option to also allow white space characters.

The alphabetic characters mean characters that makes up words in each language. However, the english alphabet is treated as the alphabetic characters in following languages: Chinese, Japanese, Korean. The language is specified by `Zend_Locale`.

## Alpha

Returns the string `$value`, removing all but alphabetic characters. This filter includes an option to also allow white space characters.

## BaseName

Given a string containing a path to a file, this filter will return the base name of the file

## Digits

Returns the string `$value`, removing all but digit characters.

## Dir

Returns directory name component of path.

## HtmlEntities

Returns the string `$value`, converting characters to their corresponding HTML entity equivalents where they exist.

## Int

Returns (int) `$value`

## StringTrim

Returns the string `$value` with characters stripped from the beginning and end.

## StripNewlines

Returns the string `$value` without any newline control characters.

## StripTags

This filter returns the input string, with all HTML and PHP tags stripped from it, except those that have been explicitly allowed. In addition to the ability to specify which tags are allowed, developers can specify which attributes are allowed across all allowed tags and for specific tags only.