get_post_meta for all keys brings back arrays, not single values

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$meta = get_post_meta($post_id,'',true);

brings back all the meta values for $post_id but it returns an array for each value, as shown below:
enter image description here

I might expect this if I had set the third parameter – single – to false but it’s set to true. I haven’t found anything in the codex that talks about what exactly is returned when key is blank.

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Does someone have to information here and know how I can get back all the keys with each key value being a single value instead of an array of values?

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2 comments

  1. The answer is: This is by design, but does not appear to be documented in the Codex.

    If you look at the true documentation (the source code), you will see that get_post_meta calls get_metadata. By inspecting the code of get_metadata, we can see that if the $meta_key is not posted, then it returns the value before it evaluates if $single is set or not:

     // Previously, $meta_cache is set to the contents of the post meta data

 // Here you see if there is no key set, it just returns it all
 if ( ! $meta_key ) {
     return $meta_cache;
 }

 // It's not until later than $single becomes a factor
 if ( isset($meta_cache[$meta_key]) ) {
    if ( $single )
        return maybe_unserialize( $meta_cache[$meta_key][0] );
    else
        return array_map('maybe_unserialize', $meta_cache[$meta_key]);
 }

    If you are using PHP 5.3+, you can get what you want with something like this:

    // Get the meta values
$meta = get_post_meta($post_id,'',true);

// Now convert them to singles
$meta = array_map(function($n) {return $n[0];}, $meta);

    Or, if you want to get really fancy, you can write your own “wrapper” around the get_post_meta function, like so:

    function get_all_post_meta($post_id) {
    // Get the meta values
    $meta = get_post_meta($post_id,'');

    // Now convert them to singles and return them
    return array_map(function($n) {return $n[0];}, $meta);
}

    Which you could then use like so: 

    $meta = get_all_post_meta($post_id);

    Or, if you aren’t on PHP 5.3+ (you should be!), you could do it like so:

    function get_all_post_meta($post_id) {
    // Get the meta values
    $meta = get_post_meta($post_id,'');

    foreach($meta AS $key => $value) {
        $meta[$key] = $value[0];
    }

    return $meta;
}

  2. I think, there is no way to get single value in get_post_meta when $single is true. So you write a custom function to get it.

    Use 

    //callback to get single value in get_meta_data
function get_single_value($val) {
    return $val[0];
}

$meta = get_post_meta($post_id,'', true);
$meta1 = array_map('get_postmeta_single_value', $meta);
print_r($meta1);

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