WordPress:使用 add_filter 时如何返回值? [英] WordPress: How to return value when use add_filter?

问题描述

我已经多次阅读 WordPress codex，但仍然不明白如果涉及多个参数时如何返回值.例如:

I've read WordPress codex many times but still don't understand how to return the value if more than one arguments involved. For example:

function bbp_get_topic_title( $topic_id = 0 ) {
    $topic_id = bbp_get_topic_id( $topic_id );
    $title    = get_the_title( $topic_id );

    return apply_filters( 'bbp_get_topic_title', $title, $topic_id );
}

在上面的过滤器中，有 2 个参数.当我 add_filter 时，我应该返回 2 个值，还是只返回我需要的一个?如果需要标题，以下示例是否正确?

In the above filter, there are 2 arguments. When I add_filter, should I return 2 value, or just return the one I need? Is the following example correct if need the title?

add_filter( 'bbp_get_topic_title', 'my_topic_title', 10, 2 );

function my_topic_title( $title, $topic_id ){
  $title = 'my_example_title';
  return $title;
}

推荐答案

完全正确.

在注册过滤器(或基本上调用 apply_filters)时，您应该使用至少两个参数调用该函数 - 要应用的过滤器的名称和将应用过滤器的值.

When registering a filter(or basically calling apply_filters), you should call the function with at least two arguments - name of the filter to be applied and the value to which the filter will be applied.

您传递给函数的任何其他参数都将传递给过滤函数，但仅如果它们请求了其他参数.举个例子:

Any further arguments that you pass to the function will be passed to the filtering functions, but only if they have requested additional arguments. Here's an example:

// Minimal usage for add_filter()
add_filter( 'my_filter', 'my_filtering_function1' );
// We added a priority for our filter - the default priority is 10
add_filter( 'my_filter', 'my_filtering_function2', 11 );
// Full usage of add_filter() - we set a priority for our function and add a number of accepted arguments.
add_filter( 'my_filter', 'my_filtering_function3', 12, 2 );

// Apply our custom filter
apply_filters( 'my_filter', 'content to be filtered', 'argument 2', 'argument 3' );

给定上面的代码，要过滤的内容将首先传递给my_filtering_function1.这个函数只会接收要过滤的内容，而不是额外的参数.

Given the code above, the content to be filtered will be passed first to my_filtering_function1. This function will only receive the content to be filtered and not the additional arguments.

然后将内容(经过my_filtering_function1处理后)传递给my_filtering_function2.同样，该函数将只接收第一个参数.

Then the content will then be passed(after being treated by my_filtering_function1) to my_filtering_function2. Again the function will only receive the first argument.

最后将内容传递给 my_filtering_function3 函数(因为它已被前两个函数更改).这次函数将改为传递 2 个参数(因为我们指定了这个)，但它不会得到 argument 3 参数.

Finally the content will be passed to the my_filtering_function3 function(as it has been changed by the previous two functions). This time the function will be passed 2 arguments instead(since we specified this), but it won't get the argument 3 argument.

参见apply_filters() 在源代码中.

See apply_filters() in source.

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