How Theme Functions Are Created

Listing 15–11. Example hook_theme() Implementation

<?php
/**
* Implements hook_theme().
*/
function mymodule_theme() { return array( 'my_theme_hook' => array( 'variables' => array('parameter' => NULL), ),  );
}
?>

Implementations of hook_theme() let Drupal know about theme hooks. Once Drupal is aware, it will search for a theme function called theme_my_theme_hook() in this case, which might look like the code inListing 15–12.

Listing 15–12. Example Theme Function Implementation

<?php
function theme_my_theme_hook($variables) { $parameter = $variables['parameter']; if (!empty($parameter)) { return '<div class="my-theme-hook">' . $parameter . '</div>'; }
}
?>

通过模块定义的主题函数可以在主题中供我们使用，极大的提供了模板的自由度，我们可以自己定义任意的主题函数，在模板中调用，如下：

<?php print theme("my-theme-hook", $vars); ?>

Calling Theme Functions

例如我们需要使用theme_image()函数，可以在api中找到它的源码：

function theme_image($variables) {$attributes = $variables['attributes'];$attributes['src'] = file_create_url($variables['path']);foreach (array('width', 'height', 'alt', 'title') as $key) {if (isset($variables[$key])) {$attributes[$key] = $variables[$key];}}return '<img' . drupal_attributes($attributes) . ' />';
}

可以看到$variables是一个二维数组，形式大概如下：

array(  'path' => '图片路径','width' => '宽度','height' => '高度','alt'  => 'alt属性','title' => '标题')

使用方法如下：

//在模板中使用下面的方法
<?php print theme('image', array('path' => 'path/to/image.png', 'alt' => 'Image
description')); ?> //千万别用这样子的方法来调用
<?php print theme_image(array('path' => 'path/to/image.png', 'alt' => 'Image description'));
?>

Overriding Theme Functions

和重载模板差不多。

1.  Find the original theme function by browsing through Drupal’s source code or 
checking http://api.drupal.org. 
2.  Copy and paste it into your template.php file. 
3.  Change the beginning of the function name from theme_ to yourthemename_. 
4.  Save template.php, clear the site cache, and reload!

■ Caution  If creating template.php from scratch, remember to include <?php at the top of the file. Also note that a closing tag should not be added at the bottom of the file. Omitting the closing PHP tag prevents unwanted whitespace, which can cause “Cannot modify header information” or “Headers already sent” errors. For more information, visit http://drupal.org/node/1424.