Chapter 5. Zend_Filter
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## Chapter 5. Zend_Filter

## 5.1. Zend_Filter

### 5.1.1. Introduction

`Zend_Filter` provides a library of static methods for filtering data. For input filtering, you should use Section 5.2, “Zend_Filter_Input” instead, because it provides a framework for filtering input using the methods provided by this class. However, because `Zend_Filter_Input` is designed primarily for arrays, `Zend_Filter` can be useful for filtering scalars, because it behaves like PHP's string functions:

        <?php

        $alphaUsername = Zend_Filter::getAlpha('John123Doe');

        /* $alphaUsername = 'JohnDoe'; */

        ?>

### 5.1.2. Use Cases

In each of these use cases, `$value` represents an arbitrary scalar value.

Whitelist Filtering:

        <?php

        if ($email = Zend_Filter::isEmail($value)) {
            /* $email is a valid email format. */
        } else {
            /* $email is not a valid email format. */
        }

        ?>

Blind Filtering:

        <?php

        $alphaName = Zend_Filter::getAlpha($value);

        ?>

Blacklist Filtering:

        <?php

        $taglessComment = Zend_Filter::noTags($value);

        ?>

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