Saving an array in a single custom field

Question

I have the following array that I want to store in a single custom field.

array("Accounting"=>"Peter", "Finance"=>"Ben", "Marketing"=>"Joe");

I want to store it by typing it in a custom field in wp-admin.

Then I want to retrieve this custom field as an array in a page, with something like

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

and Output the array with:

foreach($pos  as $x => $x_value) {
    echo $x_value . " head " . $x;
    echo "<br>";
}

My Questions are:

1. How do I save the array in a single custom field? What exactly do i have to type into the custom field?

2. How do I retrieve this custom field value as an array in a wordpress template?

Final Solution to problem thx to Ray:

1. I write the following directly into the custom field in wp admin (or use update_post_meta with json_encode in template)

   {"Accounting":"Peter","Finance":"Ben","Marketing":"Joe"}
   

2. Retrieve array in custom field with:

   $json_data = get_post_meta($post_id, "my_custom_meta_key", true);
   $arr_data = json_decode($json_data, true);
   

Answer 1

You can json_encode() it which will make it a string that you can put into a custom field then just ensure you json_decode() it to bring it back to an object or json_decode($data, true) to bring it back as an array

$arr = array("Accounting"=>"Peter", "Finance"=>"Ben", "Marketing"=>"Joe");
update_post_meta($post_id, "my_custom_meta_key", json_encode($arr));
$json_data = get_post_meta($post_id, "my_custom_meta_key", true); // true to ensure it comes back as a string and not an array
$arr_data = json_decode($json_data, true); // 2nd parameter == true so it comes back as an array();

Answer 2

Usually, custom fields are save from form input. If you want to save an array like yours, you can create a metabox on the post edit screen.

This metabox should display input with the same name, something like that

<input type="text" name="pos[Accounting]" value=""/>
<input type="text" name="pos[Finance]" value=""/>
<input type="text" name="pos[Marketing]" value=""/>

The way you suggest to display looks good.

You can find more details to display and save metaboxes with add_meta_boxes action et add_meta_box()

hope it gives you some hints !

Answer 3

Sounds like you want to be able to input these values from the core WordPress custom fields metabox:

To do this I would use a custom format, and then convert it when the post is saved.

// This function converts "Accounting,Peter|Finance,Ben|Marketing,Joe" format
// to array("Accounting"=>"Peter", "Finance"=>"Ben", "Marketing"=>"Joe");
function smyles_convert_custom_format_to_array( $val ){

    $employee_data = array();

    // Create array with | as separator
    $parts = explode( '|', $val );

    if( ! empty( $parts ) ){

        // Loop through each one
        foreach( $parts as $part ){

            // Split again based on comma
            $part_array = explode( ',', $part );

            // As long as there is a value, let's add it to our employee array
            if( ! empty( $part_array[0] ) && ! empty( $part_array[1] ) ){

                // First value in array will be our key, second will be the value
                $employee_data[ $part_array[0] ] = $part_array[1];
            }

        }

    }

    return $employee_data;
}

You then need to add an action to update the meta after converting the custom format with the function above:

// Add a custom action on save post so we can convert our custom format
add_action( 'save_post', 'smyles_save_post_format_custom_field', 99, 3 );
// This function will update the post meta with an array instead of using our custom format
function smyles_save_post_format_custom_field( $id, $post, $update ){

    $custom_field = 'employees';

    // Change `post` below to something else if using custom post type
    if( $post->post_type != 'post' ) {
        return;
    }

    // Only try to process if a value exists
    if( ! empty( $_POST[ $custom_field ] ) ){
        $value = smyles_convert_custom_format_to_array( $_POST[ $custom_field ] );
    } else {
        // Otherwise set $value to empty value, meaning custom field was deleted or has an empty value
        $value = array();
    }

    update_post_meta( $id, $custom_field, $value, true );

}

When you want to pull these values, just use this:

// Arrays are stored serialized, so let's get that first
$value = get_post_meta( $post_id, 'employees', true);

Voila! Profit!