Zend Framework by examples (ZfEx): Text filtering

In this example, we implement text filtering. Filters are chained together. We also implement custom filters.

Components used in this example

MyFilter MyBin2HexFilter MyHex2BinFilter MyHtml Entry point HTML | Try it | View source code

Implementation of the filtering process

We define the list of Zend filters. We exclude the filters where parameters are needed. We also exclude the filters on files.
We define the list of custom filters.
We define the encryption adapter and the encryption key.


class MyFilter
{
    // We define the list of Zend filters.
    // We exclude the filters where parameters are needed.
    // We also exclude the filters on files.
    public $zendFilters = array(
        'Zend_Filter_Alnum',
        'Zend_Filter_Alpha',
        'Zend_Filter_BaseName',
        // 'Zend_Filter_Callback',
        'Zend_Filter_Decrypt',
        'Zend_Filter_Digits',
        'Zend_Filter_Dir',
        'Zend_Filter_Encrypt',
        // 'Zend_Filter_Encrypt_Mcrypt',
        // 'Zend_Filter_Encrypt_Openssl',
        // 'Zend_Filter_File_Decrypt',
        // 'Zend_Filter_File_Encrypt',
        // 'Zend_Filter_File_LowerCase',
        // 'Zend_Filter_File_Rename',
        // 'Zend_Filter_File_UpperCase',
        'Zend_Filter_HtmlEntities',
        'Zend_Filter_Int',
        'Zend_Filter_LocalizedToNormalized',
        'Zend_Filter_NormalizedToLocalized',
        // 'Zend_Filter_PregReplace',
        // 'Zend_Filter_RealPath',
        'Zend_Filter_StringToLower',
        'Zend_Filter_StringToUpper',
        // 'Zend_Filter_StringTrim',
        'Zend_Filter_StripNewlines',
        'Zend_Filter_StripTags',
        'Zend_Filter_Word_CamelCaseToDash',
        'Zend_Filter_Word_CamelCaseToSeparator',
        'Zend_Filter_Word_CamelCaseToUnderscore',
        'Zend_Filter_Word_DashToCamelCase',
        'Zend_Filter_Word_DashToSeparator',
        'Zend_Filter_Word_DashToUnderscore',
        'Zend_Filter_Word_SeparatorToCamelCase',
        'Zend_Filter_Word_SeparatorToDash',
        // 'Zend_Filter_Word_SeparatorToSeparator',
        'Zend_Filter_Word_UnderscoreToCamelCase',
        'Zend_Filter_Word_UnderscoreToDash',
        'Zend_Filter_Word_UnderscoreToSeparator',
    );

    // We define the list of custom filters.
    public $customFilters = array(
        'MyBin2HexFilter',
        'MyHex2BinFilter',
    );

    // We define the encryption adapter and the encryption key.
    private $_encryption = array('adapter' => 'mcrypt', 'key' => 'the key');

Text filtering

We get the text, the filters, and the encryption vector, from the GET request.
We instantiate the filter chain.
If the filter is an encryption filter, we instantiate the filter.
And we get the initialization vector.
Then we add the encryption filter.
And we add the filter to convert the encrypted text into a hexadecimal string.
If the filter is an decryption filter, we instantiate the filter.
And we pass the initialization vector.
Then we add the filter to convert the encrypted text into a binary string.
And we add the decryption filter.
If this is any other filter, we just add the filter.
We apply the filters to the text.
If we catch an exception, we return the error message.


    public function process()
    {
        // We get the text, the filters, and the encryption vector, from the GET request.
        list($data, $filters, $vector) = $this->_getParameters();

        try {
            if (empty($data) or empty($filters)) {
                $result = 'Please enter some text and select one or more filters!';
            } else {
                // We instantiate the filter chain.
                $filterChain = new Zend_Filter();

                foreach($filters as $filter) {
                    switch ($filter) {
                        case 'Zend_Filter_Encrypt':
                            // If the filter is an encryption filter,
                            // we instantiate the filter.
                            $encrypt = new Zend_Filter_Encrypt($this->_encryption);
                            // And we get the initialization vector.
                            $vector = bin2hex($encrypt->getVector());
                            // Then we add the encryption filter.
                            $filterChain->addFilter($encrypt);
                            // And we add the filter to convert the encrypted text
                            // into a hexadecimal string.
                            $filterChain->addFilter(new MyBin2HexFilter);
                            break;

                        case 'Zend_Filter_Decrypt':
                            // If the filter is an decryption filter,
                            // we instantiate the filter.
                            $decrypt = new Zend_Filter_Decrypt($this->_encryption);
                            // And we pass the initialization vector.
                            $decrypt->setVector(hex2bin($vector));
                            // Then we add the filter to convert the encrypted text
                            // into a binary string.
                            $filterChain->addFilter(new MyHex2BinFilter);
                            // And we add the decryption filter.
                            $filterChain->addFilter($decrypt);
                            break;

                        default:
                            // If this is any other filter, we just add the filter.
                            $filterChain->addFilter(new $filter());
                    }
                }

                // We apply the filters to the text.
                $result = $filterChain->filter($data);
            }


        } catch (Exception $e) {
            // If we catch an exception, we return the error message.
            $result = $e->getMessage();
        }

        $filters = array_pad($filters, 3, null);

        return array($data, $filters, $vector, $result);
    }

Extraction of the parameters from the GET request

We ignore a filter if the filter is invalid.


    private function _getParameters()
    {
        $data = isset($_GET['data'])? $_GET['data'] : null;
        $vector = isset($_GET['vector'])? $_GET['vector'] : null;

        // We ignore a filter if the filter is invalid.
            $filters = array();
        if (isset($_GET['filters'])) {
            foreach($_GET['filters'] as $filter) {
                (in_array($filter, $this->zendFilters) or
                in_array($filter, $this->customFilters)) and
                $filters[] = $filter;
            }
        }

        return array($data, $filters, $vector);
    }

Creation of a filter to convert a string from hexadecimal into binary


class MyBin2HexFilter implements Zend_Filter_Interface
{
    public function filter($bin)
    {
        return bin2hex($bin);
    }

Creation of a filter to convert a string from binary into hexadecimal


class MyHex2BinFilter implements Zend_Filter_Interface
{
    public function filter($hex)
    {
        return hex2bin($hex);
    }

Displaying items


class MyHtml
{

Displaying the title of the page based on the file name.


    public static function printTitle()
    {
        $basename = basename(__FILE__, '.php');
        $title = ucwords(str_replace('-' , ' ', $basename));
        $zfVersion = Zend_Version::VERSION;
        $phpVersion = phpversion();
        echo "ZfEx $title (ZF/$zfVersion PHP/$phpVersion)";
    }

Displaying the selected option


    public static function printSelected($value, $target)
    {
        $value == $target and print 'selected="selected"';
    }

Displaying a string or an array

If the data is an array, we convert the array into a set of lines.
We converts special characters into HTML entities.
We convert new-line characters into line breaks.


    public static function display($mixed, $isNl2Br = true)
    {
        // If the data is an array, we convert the array into a set of lines.
        is_array($mixed) and $mixed = implode("\n", $mixed);
        $mixed = stripslashes($mixed);
        // We converts special characters into HTML entities.
        $mixed = htmlspecialchars($mixed, ENT_QUOTES, 'UTF-8');
        // We convert new-line characters into line breaks.
        $isNl2Br and $mixed = nl2br($mixed);
        echo $mixed;
    }

Colorization of data

We export the data as valid PHP code.
We add the PHP tag, we colorize the code, we remove the PHP tag.
We display the data.


    public static function colorize($mixed)
    {
        // We export the data as valid PHP code.
        $mixed = var_export($mixed, true);
        // We add the PHP tag, we colorize the code, we remove the PHP tag.
        $mixed = '<?' . "php $mixed";
        $mixed = highlight_string($mixed, true);
        $mixed = str_replace('&lt;?php&nbsp;', '', $mixed);
        // We display the data.
        echo "<pre>$mixed</pre>";
    }

Filtering the text

We apply the filters to the text and we get all the parameters and the result, to display in the form.


// We apply the filters to the text and we get all the parameters and the result,
// to display in the form.
$filter = new MyFilter();
list($data, $filters, $vector, $result) = $filter->process();


<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title><?php MyHtml::printTitle();?></title>
    <style type="text/css">
      body, td {
          font-family: arial, sans-serif;
          font-size: 0.9em;
      }
      textarea.data {
          height: 5em;
          width: 30em;
      }
    </style>
  </head>

  <body>

    <p>EXAMPLE <?php MyHtml::printTitle();?></p>
    <hr />

    <form name="form">

      <input type="hidden" name="vector" value="<?php MyHtml::display($vector);?>" />
      <table>

        <tr>
          <td>Text</td>
          <td><textarea class="data" name="data"><?php MyHtml::display($data, false);?></textarea></td>
        </tr>

        <tr><td>&nbsp;</td></tr>

        <tr>
          <td>Filter Chain</td>
          <td>
            <select name="filters[0]">
              <option></option>
              <optgroup label="Zend Filters">
                <?php foreach($filter->zendFilters as $name) :?>
                    <option value="<?php echo $name;?>"
                            <?php MyHtml::printSelected($filters[0], $name);?>>
                      <?php echo $name;?>
                    </option>
                <?php endforeach;?>
              </optgroup>
              <optgroup label="Custom Filters">
                <?php foreach($filter->customFilters as $name) :?>
                    <option value="<?php echo $name;?>"
                            <?php MyHtml::printSelected($filters[0], $name);?>>
                      <?php echo $name;?>
                    </option>
                <?php endforeach;?>
              </optgroup>
            </select>
          </td>
        </tr>

        <tr>
          <td></td>
          <td>
            <select name="filters[1]">
              <option></option>
              <optgroup label="Zend Filters">
                <?php foreach($filter->zendFilters as $name) :?>
                    <option value="<?php echo $name;?>"
                            <?php MyHtml::printSelected($filters[1], $name);?>>
                      <?php echo $name;?>
                    </option>
                <?php endforeach;?>
              </optgroup>
              <optgroup label="Custom Filters">
                <?php foreach($filter->customFilters as $name) :?>
                    <option value="<?php echo $name;?>"
                            <?php MyHtml::printSelected($filters[1], $name);?>>
                      <?php echo $name;?>
                    </option>
                <?php endforeach;?>
              </optgroup>
            </select>
          </td>
        </tr>

        <tr>
          <td></td>
          <td>
            <select name="filters[2]">
              <option></option>
              <optgroup label="Zend Filters">
                <?php foreach($filter->zendFilters as $name) :?>
                    <option value="<?php echo $name;?>"
                            <?php MyHtml::printSelected($filters[2], $name);?>>
                      <?php echo $name;?>
                    </option>
                <?php endforeach;?>
              </optgroup>
              <optgroup label="Custom Filters">
                <?php foreach($filter->customFilters as $name) :?>
                    <option value="<?php echo $name;?>"
                            <?php MyHtml::printSelected($filters[2], $name);?>>
                      <?php echo $name;?>
                    </option>
                <?php endforeach;?>
              </optgroup>
           </select>
          </td>
        </tr>

        <tr><td>&nbsp;</td></tr>

        <tr>
          <td></td>
          <td><input type="submit" value="Submit" /></td>
          <td>MyBin2Hex is always applied after Zend_Filter_Encrypt because it returns a binary string.
              <br />
              MyHex2Bin is always applied before Zend_Filter_Decrypt because it needs a binary string.
          </td>
        </tr>

      </table>
    </form>

    <hr />
    RESULT
    <br /> <br />
    <?php MyHtml::display($result);?>

  </body>
</html>