我有一个动作钩，它非常适合于\\u内容。我想在任何时候请求一些custom\\u字段时应用相同的钩子。

自定义字段是1）myfieldone 2）myfieldart 3）myfieldestionSo让我们只取其中一个-“myfieldone”有没有办法-在任何时候请求“myfieldone”自定义字段时，我都可以过滤该自定义字段的值（内容）？

我想这很简单

add_filter(\'myfieldone\', \'my_add_a_class_function\', 10,8);
//or 
add_action(\'myfieldone\', \'my_add_a_class_function\');

然而，这两者都没有任何效果。

我还尝试将其全局应用于所有get\\u meta、get\\u meta\\u key

add_filter(\'get_meta\', \'my_add_a_class_function\', 10,8);
add_filter(\'get_meta_key\', \'my_add_a_class_function\', 10,8);
//no such luck. What am I missing?

所以我基本上想

$which_meta_key = \'myfieldone\';
add_action($which_meta_key, \'my_add_a_class_function\');

下面是我如何处理\\u内容的。

add_action(\'the_content\', \'my_add_a_class_function\');
function my_add_a_class_function($content){

    $sample_html = $content;    

// grab all the matches for img tags and exit if there aren\'t any
if(!preg_match_all(\'/<img.*\\/>/i\', $sample_html, $matches))
  exit("Found no img tags that need fixing\\n");

// check out all the image tags we found (stored in index 0)
//print_r($matches);

// iterate through the results and run replaces where needed
foreach($matches[0] as $string){
    // keep this for later so that we can replace the original with the fixed one
    $original_string = $string;

    // preg_replace only replaces stuff when it matches a pattern so it\'s safe to
    // just run even if it wont do anything.

    $classes = \'TEST\'; // separated by spaces, e.g. \'img image-link\'
    // check if there are already classes assigned to the anchor
    if ( preg_match(\'/<img.*? class=".*?">/\', $string) ) {
      $string = preg_replace(\'/(<img.*? class=".*?)(".*?>)/\', \'$1 \' . $classes . \'$2\', $string);
    } else {
      $string = preg_replace(\'/(<img.*?)>/\', \'$1 class="\' . $classes . \'" >\', $string);
    }

    // now replace the original occurence in the html with the fix
    $sample_html = str_replace($original_string, $string, $sample_html);  

} 

return $sample_html;    
}

UPDATE:下面的自定义元键调用似乎工作正常。然而，我收到了“未找到需要修复的img标记”{if/EXIT}消息

... // pass the custom_meta content to my filter. 
$sample_content = $content
print_r($sample_content);

//YIELDS
    <p><img class="alignleft" width="175" height="175" src="/wp-content/uploads/2013/04/brother-in-law.gif" alt="">
Peter, My brother-in-law informed me that he has a new job at IBM.</p>

但是，在应用过滤器之前，我会检查是否有要过滤的图像。如果不存在，则存在。显然，没有找到任何图像-尽管通过print\\r-图像标签明显存在。

if(!preg_match_all(\'/<img.*\\/>/i\', $sample_html, $matches))
  exit("Found no img tags that need fixing\\n");

// YIELDS:
Found no img tags that need fixing

//however it does echo out my custom field html code, the image and paragraph text display - - because thats part of the get_meta_data - where I initially request the custom field.

SO - QUESTION - 这是一个简单的正则表达式问题吗？我的

preg_match_all (\'/<img.*\\/>/i\'...

OR - 我是否需要对内容应用“to\\u string”过滤器，以便它将图像作为图像而不仅仅是文本查找

function wpse94639_get_post_meta( $post_id, $key = \'\', $single = false ) {
    $metadata = get_post_meta( $post_id, $key, $single );
    return apply_filters( \'wpse94639\', $metadata );
}

$meta_value = get_post_meta($post_id,\'key\');
$meta_value = my_add_a_class_function($meta_value);