Filter an array with a callback - for single & multidimensional arrays

Question

I've a filter attached, that allows modifying an array:

$data = apply_filters( 'wpse_example_filter', $data );

The problem is, that the data can be a single or multidimensional array:

// single:
'SINGLE' => array(
    // some data
)
// multidimensional:
'MULTI' => array(
     0 => array(
         // some data
     )
     1 => array(
         // some data
     )
)

Question: What's the easiest way to loop through the data of one of those arrays (inside my callback), without knowing if I got a single or multidimensional array and without creating another callback function?

In other words: How would I write a recursive filter callback?

Have you tried using the array_walk_recursive function in PHP? php.net/manual/en/function.array-walk-recursive.php — Otto
– Otto, Commented Aug 31, 2012 at 17:07
That wasn't an answer in and of itself, I was asking for clarification. Your particular situation may not be suited to using that function, since I don't know exactly what you're trying to do with the data. — Otto
– Otto, Commented Aug 31, 2012 at 17:26
Imagine above filter to be in some 3rd party plugin. Below array (SINGLE/MULTI) is what is inside $data. I'm then writing another plugin to modify the $data, array by array - or just a single one. — kaiser
– kaiser, Commented Aug 31, 2012 at 17:51

kaiser · Accepted Answer · 2012-08-31 12:47:10Z

3

While your answer is very interesting and I like it, I still want to post another proposal, just let you have another choice :)

IMHO, if the data contains only simple fields, like:

array(
    'name' => 'my name',
    'address' => 'my address',
    'phone' => '01234',
);

then you can use the code below:

add_filter( 'wpse63692_example_filter', 'wpse63692_example_cb' );

function wpse63692_example_cb( $data )
{
    foreach ( $data as $key => $value )
    {
        // Recursively apply filters to sub array
        if ( is_array( $value ) )
            $data[$key] = apply_filters( current_filter(), $value );
    }

    // Do something with $data

    return $data;
}

edited Aug 31, 2012 at 12:47

kaiser

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answered Aug 31, 2012 at 7:01

Anh Tran

4,1721 gold badge28 silver badges36 bronze badges

1

+1 :) I hope you don't mind the edit. One sidenote: is_array() will also trigger sub-sub-sub-arrays and fail in this case (where one wants to not touch the sub array.

kaiser
– kaiser

2012-08-31 12:47:29 +00:00
Commented Aug 31, 2012 at 12:47
1

I like your current_filter function! Thanks for editing for me :)

Anh Tran
– Anh Tran

2012-08-31 15:56:46 +00:00
Commented Aug 31, 2012 at 15:56

Add a comment |

kaiser · Accepted Answer · 2012-11-26 03:19:41Z

This is what I've found so far.

The trick is, that I'm using a non existent 2^nd argument named $recursive to determine if I'm in a recursive loop or not. The default value is false, so the $is_multiple loop gets triggered. I'm then passing a true to the function call, to disallow a loop through possibly present sub-sub-arrays.

The only reason why this is possible, is that the filter/action API doesn't start crying when I got more arguments for my function, than apply_filters() has.

function wpse63692_example_cb( $data, $recursive = false )
{
    $result = $data;
    if ( 1 < count( $data ) AND ! $recursive )
    {
        $result = array();
        foreach ( $data as $key => $value )
            $result[ $key ] = call_user_func( __FUNCTION__, $value, true );
    }

    return $result;
}
add_filter( 'wpse63692_example_filter', 'wpse63692_example_cb' );

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