apply_filters only adding second add_filter function

Question

Here's my apply_filters function to return select box options:

function my_shortcode_filters(){
    $handle = ''; $value = apply_filters('my_add_shortcode', $handle);
    if($value) $handle = "<option value='$value'>$value</option>"; 
    return $handle;
}

Here's the html where I call the function:

<select id="my-selectbox">
    <?php echo my_shortcode_filters(); ?>
    <option value="">1</option>
    <option value="2">2</option>
    <option value="3">3</option>
</select>

And here are the add_filter functions I'm testing with:

add_filter('my_add_shortcode', 'yourprefix_new_sc_handle', 10);
function yourprefix_new_sc_handle(){
    return 'myhandle';  
}
add_filter('my_add_shortcode', 'yourprefix_new_sc_handle2', 11);
function yourprefix_new_sc_handle2(){
    return 'myhandle2'; 
}

But only the second add_filter function is added to the dropdown menu. If I remove the second function, the first one is added. But when I add the second function, it overwrites the first add_filter. What am I missing here?

Ben May Ben May · Accepted Answer · 2014-04-19T03:33:12

Filters are designed to filter content, not just return a value.

IE, you start with a variable being a value of something, then the filters manipulate that value until all filters have been applied and you end up with the final value.

EG:

add_filter( 'my_x', 'test_one' );

function test_one( $var ) {
   return $var . 'y';
}

$var = 'x';

echo apply_filters( 'my_x', $var );

Result: xy as it takes x then appends y to it.

Your above code is doing a return, not doing any actual filtering - thus you're having the error where the last function to run is the result you see.

What I think you're trying to do (and I could be wrong) is using actions, not filters.

Look into add_action() and do_action() and see if that helps.

apply_filters only adding second add_filter function

1 Answers