Aneka Variasi WP Custom Meta Box di WP-Admin

Sumber:
https://code.tutsplus.com/articles/reusable-custom-meta-boxes-part-1-intro-and-basic-fields--wp-23259
https://code.tutsplus.com/articles/reusable-custom-meta-boxes-part-2-advanced-fields--wp-23293


// Add the Meta Box --->> Create a Meta Box
function add_custom_meta_box() {
    add_meta_box(
        'custom_meta_box', // $id
        'Custom Meta Box', // $title
        'show_custom_meta_box', // $callback
        'post', // $page
        'normal', // $context
        'high'); // $priority
}
add_action('add_meta_boxes', 'add_custom_meta_box');

// Field Array -->> Create the Field Array
$prefix = 'custom_';
$custom_meta_fields = array(
    array(
        'label'=> 'Text Input',
        'desc'  => 'A description for the field.',
        'id'    => $prefix.'text',
        'type'  => 'text'
    ),
    array(
        'label'=> 'Textarea',
        'desc'  => 'A description for the field.',
        'id'    => $prefix.'textarea',
        'type'  => 'textarea'
    ),
    array(
        'label'=> 'Checkbox Input',
        'desc'  => 'A description for the field.',
        'id'    => $prefix.'checkbox',
        'type'  => 'checkbox'
    ),
    array(
        'label'=> 'Select Box',
        'desc'  => 'A description for the field.',
        'id'    => $prefix.'select',
        'type'  => 'select',
        'options' => array (
            'one' => array (
                'label' => 'Option One',
                'value' => 'one'
            ),
            'two' => array (
                'label' => 'Option Two',
                'value' => 'two'
            ),
            'three' => array (
                'label' => 'Option Three',
                'value' => 'three'
            )
        )
    )
);

// The Callback -->> Outputting the Fields
function show_custom_meta_box() {
global $custom_meta_fields, $post;
// Use nonce for verification
echo '<input type="hidden" name="custom_meta_box_nonce" value="'.wp_create_nonce(basename(__FILE__)).'" />';

    // Begin the field table and loop
    echo '<table class="form-table">';
    foreach ($custom_meta_fields as $field) {
        // get value of this field if it exists for this post
        $meta = get_post_meta($post->ID, $field['id'], true);
        // begin a table row with
        echo '<tr>
                <th><label for="'.$field['id'].'">'.$field['label'].'</label></th>
                <td>';
                switch($field['type']) {




                 // TEXT
case 'text':
    echo '<input type="text" name="'.$field['id'].'" id="'.$field['id'].'" value="'.$meta.'" size="30" />
        <br /><span class="description">'.$field['desc'].'</span>';
break;

// TEXT AREA
case 'textarea':
    echo '<textarea name="'.$field['id'].'" id="'.$field['id'].'" cols="60" rows="4">'.$meta.'</textarea>
        <br /><span class="description">'.$field['desc'].'</span>';
break;

// CHECK BOX
case 'checkbox':
    echo '<input type="checkbox" name="'.$field['id'].'" id="'.$field['id'].'" ',$meta ? ' checked="checked"' : '','/>
        <label for="'.$field['id'].'">'.$field['desc'].'</label>';
break;

// SELECT BOX
case 'select':
    echo '<select name="'.$field['id'].'" id="'.$field['id'].'">';
    foreach ($field['options'] as $option) {
        echo '<option', $meta == $option['value'] ? ' selected="selected"' : '', ' value="'.$option['value'].'">'.$option['label'].'</option>';
    }
    echo '</select><br /><span class="description">'.$field['desc'].'</span>';
break;





                } //end switch
        echo '</td></tr>';
    } // end foreach
    echo '</table>'; // end table
}



// SAVE THE DATA
function save_custom_meta($post_id) {
    global $custom_meta_fields;

    // verify nonce
    if (!wp_verify_nonce($_POST['custom_meta_box_nonce'], basename(__FILE__)))
        return $post_id;
    // check autosave
    if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE)
        return $post_id;
    // check permissions
    if ('page' == $_POST['post_type']) {
        if (!current_user_can('edit_page', $post_id))
            return $post_id;
        } elseif (!current_user_can('edit_post', $post_id)) {
            return $post_id;
    }
    // loop through fields and save the data
    foreach ($custom_meta_fields as $field) {
        $old = get_post_meta($post_id, $field['id'], true);
        $new = $_POST[$field['id']];
        if ($new && $new != $old) {
            update_post_meta($post_id, $field['id'], $new);
        } elseif ('' == $new && $old) {
            delete_post_meta($post_id, $field['id'], $old);
        }
    } // end foreach
}
add_action('save_post', 'save_custom_meta');