WordPress Plugin — Add Dynamic Meta Boxes

This particular solution is for the Agent theme from StudioPress. If you are not using that theme you may find it less useful. Here's a solution I used for a client which replaced the Write Post Panel Plugin written by Nathan Rice. Under his solution, adding new boxes required using the add_meta_box() WordPress function. Each field is then created by copying and pasting sections of code. I thought to myself, "The program could do all that and free me from that chore." Before writing a solution I trotted over to the StudioPress Support forum to see if anyone had presented a similar solution. Turns out that many people there were having a hard time understanding what they had to edit and to copy. Well, you don't have to hit me over the head with a 2-by-4 (usually) before I get a clue. My solution uses a data structure. The programmer only needs to define the data structure and the code tears that apart behind the scene. To add a box we only need to add a new array of arrays to the data structure. Here's an example:
PLAIN TEXT
PHP:
  1. $sp_boxes = array (
  2.     'Property Details' => array (
  3.         array( '_square_feet', 'Square Feet:' ),
  4.         array( '_bedrooms', 'Bedrooms:' ),
  5.         array( '_basement', 'Basement (full, 1/2, finished, unfinished):' ),
  6.         array( '_addtional_features', 'Additional Features:', 'textarea' ),
  7.     ),
  8. );

This data structure tells the script to set up a form similar to this (this isn't exactly it because I am too lazy to find the css in the admin section which controls this stuff):

Property Details
















Perhaps, more importantly, this produces the exact same thing we might have done previously with some editing, copying, pasting and, potentially, human error. Below is a listing of the replacement for the Nathan Rice Plugin file: write-panel.php. You can find a file version here. It's on another web site. I'll move it over to this one soon. I am working on a full Plugin, but it will need to include a page template drop down that is not included here and I'd like to make it a PHP class. Feel free to leave comments at the bottom of this page. (You may need a user account to comment.)
PLAIN TEXT
PHP:
  1. <?php
  2. /*
  3.     Plugin Name: Add Dynamic Meta Boxes
  4.     Plugin URI: http://www.clarksonenergyhomes.com/wordpress/wordpress-plugin-add-dynamic-meta-boxes/
  5.     Description: Allows you to add boxes and fields to the Write Post panel, and store the value as a custom field. Based on script by Nathan Rice (http://www.nathanrice.net/)
  6.     Version: 0.1 (Not rigorously tested.)
  7.     Author: Charles Clarkson
  8.     Author URI: http://www.clarksonenergyhomes.com/wordpress/about/
  9. */
  10.  
  11. /*
  12.     Each box has a name and a set of fields. Currently,
  13.     only text and textarea fields are suppoted. 'text'
  14.     fields are the default.
  16.     To add a box named: "Name Box" with a field named
  17.     "_name", add this:
  19.     'Name Box' => array (
  20.         array( '_name', 'Name:', 'text' ),
  21.     ),
  23.     You can leave the 'text' field off. It is the default.
  25.     'Name Box' => array (
  26.         array( '_name', 'Name:' ),
  27.     ),
  28. */
  29.  
  30. // Edit this data structure to change the form in WordPress:
  31.  
  32. $sp_boxes = array (
  33.     'General Property Info' => array (
  34.         array( '_listing_price', 'Listing Price:' ),
  35.         array( '_mls', 'MLS # (if any):' ),
  36.         array( '_address', 'Address:' ),
  37.         array( '_city', 'City:' ),
  38.         array( '_state', 'State:' ),
  39.         array( '_zip_code', 'Zip Code:' ),
  40.     ),
  41.     'Property Details' => array (
  42.         array( '_square_feet', 'Square Feet:' ),
  43.         array( '_bedrooms', 'Bedrooms:' ),
  44.         array( '_basement', 'Basement (full, 1/2, finished, unfinished):' ),
  45.         array( '_addtional_features', 'Additional Features:', 'textarea' ),
  46.     ),
  47.     'Property Photos' => array (
  48.         array( '_photo_1_large', 'Photo #1 large URL:' ),
  49.         array( '_photo_1_thumbnail', 'Photo #1 thumbnail URL:' ),
  50.         array( '_photo_2_large', 'Photo #2 large URL:' ),
  51.         array( '_photo_2_thumbnail', 'Photo #2 thumbnail URL:' ),
  52.         array( '_photo_3_large', 'Photo #3 large URL:' ),
  53.         array( '_photo_3_thumbnail', 'Photo #3 thumbnail URL:' ),
  54.         array( '_photo_4_large', 'Photo #4 large URL:' ),
  55.         array( '_photo_4_thumbnail', 'Photo #4 thumbnail URL:' ),
  56.         array( '_photo_5_large', 'Photo #5 large URL:' ),
  57.         array( '_photo_5_thumbnail', 'Photo #5 thumbnail URL:' ),
  58.         array( '_photo_6_large', 'Photo #6 large URL:' ),
  59.         array( '_photo_6_thumbnail', 'Photo #6 thumbnail URL:' ),
  60.     ),
  61. );
  62.  
  63. // Do not edit past this point.
  64.  
  65. // Use the admin_menu action to define the custom boxes
  66. add_action( 'admin_menu', 'sp_add_custom_box' );
  67.  
  68. // Use the save_post action to do something with the data entered
  69. // Save the custom fields
  70. add_action( 'save_post', 'sp_save_postdata', 1, 2 );
  71.  
  72. // Adds a custom section to the "advanced" Post and Page edit screens
  73. function sp_add_custom_box() {
  74.     global $sp_boxes;
  75.  
  76.     if ( function_exists( 'add_meta_box' ) ) {
  77.  
  78.         foreach ( array_keys( $sp_boxes ) as $box_name ) {
  79.             add_meta_box( $box_name, __( $box_name, 'sp' ), 'sp_post_custom_box', 'post', 'normal', 'high' );
  80.         }
  81.     }
  82. }
  83.  
  84. function sp_post_custom_box ( $obj, $box ) {
  85.     global $sp_boxes;
  86.     static $sp_nonce_flag = false;
  87.  
  88.     // Run once
  89.     if ( ! $sp_nonce_flag ) {
  90.         echo_sp_nonce();
  91.         $sp_nonce_flag = true;
  92.     }
  93.  
  94.     // Genrate box contents
  95.     foreach ( $sp_boxes[$box['id']] as $sp_box ) {
  96.         echo field_html( $sp_box );
  97.     }
  98. }
  99.  
  100. function field_html ( $args ) {
  101.  
  102.     switch ( $args[2] ) {
  103.  
  104.         case 'textarea':
  105.             return text_area( $args );
  106.  
  107.         case 'checkbox':
  108.             // To Do
  109.  
  110.         case 'radio':
  111.             // To Do
  112.  
  113.         case 'text':
  114.         default:
  115.             return text_field( $args );
  116.     }
  117. }
  118.  
  119. function text_field ( $args ) {
  120.     global $post;
  121.  
  122.     // adjust data
  123.     $args[2] = get_post_meta($post->ID, $args[0], true);
  124.     $args[1] = __($args[1], 'sp' );
  125.  
  126.     $label_format =
  127.           '<label for="%1$s">%2$s</label><br />'
  128.         . '<input style="width: 95%%;" type="text" name="%1$s" value="%3$s" /><br /><br />';
  129.  
  130.     return vsprintf( $label_format, $args );
  131. }
  132.  
  133. function text_area ( $args ) {
  134.     global $post;
  135.  
  136.     // adjust data
  137.     $args[2] = get_post_meta($post->ID, $args[0], true);
  138.     $args[1] = __($args[1], 'sp' );
  139.  
  140.     $label_format =
  141.           '<label for="%1$s">%2$s</label><br />'
  142.         . '<textarea style="width: 95%%;" name="%1$s">%3$s</textarea><br /><br />';
  143.  
  144.     return vsprintf( $label_format, $args );
  145. }
  146.  
  147. /* When the post is saved, saves our custom data */
  148. function sp_save_postdata($post_id, $post) {
  149.     global $sp_boxes;
  150.  
  151.     // verify this came from the our screen and with proper authorization,
  152.     // because save_post can be triggered at other times
  153.     if ( ! wp_verify_nonce( $_POST['sp_nonce_name'], plugin_basename(__FILE__) ) ) {
  154.         return $post->ID;
  155.     }
  156.  
  157.     // Is the user allowed to edit the post or page?
  158.     if ( 'page' == $_POST['post_type'] ) {
  159.         if ( ! current_user_can( 'edit_page', $post->ID ))
  160.             return $post->ID;
  161.  
  162.     } else {
  163.         if ( ! current_user_can( 'edit_post', $post->ID ))
  164.             return $post->ID;
  165.     }
  166.  
  167.     // OK, we're authenticated: we need to find and save the data
  168.     // We'll put it into an array to make it easier to loop though.
  169.  
  170.     // The data is already in $sp_boxes, but we need to flatten it out.
  171.     foreach ( $sp_boxes as $sp_box ) {
  172.         foreach ( $sp_box as $sp_fields ) {
  173.             $my_data[$sp_fields[0]] =  $_POST[$sp_fields[0]];
  174.         }
  175.     }
  176.  
  177.     // Add values of $my_data as custom fields
  178.     // Let's cycle through the $my_data array!
  179.     foreach ($my_data as $key => $value) {
  180.         if ( 'revision' == $post->post_type  ) {
  181.             // don't store custom data twice
  182.             return;
  183.         }
  184.  
  185.         // if $value is an array, make it a CSV (unlikely)
  186.         $value = implode(',', (array)$value);
  187.  
  188.         if ( get_post_meta($post->ID, $key, FALSE) ) {
  189.  
  190.             // Custom field has a value.
  191.             update_post_meta($post->ID, $key, $value);
  192.  
  193.  
  194.         } else {
  195.  
  196.             // Custom field does not have a value.
  197.             add_post_meta($post->ID, $key, $value);
  198.         }
  199.  
  200.         if (!$value) {
  201.  
  202.             // delete blanks
  203.             delete_post_meta($post->ID, $key);
  204.         }
  205.     }
  206. }
  207.  
  208. function echo_sp_nonce () {
  209.  
  210.     // Use nonce for verification ... ONLY USE ONCE!
  211.     echo sprintf(
  212.         '<input type="hidden" name="%1$s" id="%1$s" value="%2$s" />',
  213.         'sp_nonce_name',
  214.         wp_create_nonce( plugin_basename(__FILE__) )
  215.     );
  216. }
  217.  
  218. // A simple function to get data stored in a custom field
  219. if ( !function_exists('get_custom_field') ) {
  220.     function get_custom_field($field) {
  221.        global $post;
  222.        $custom_field = get_post_meta($post->ID, $field, true);
  223.        echo $custom_field;
  224.     }
  225. }
  226.  
  227. ?>

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