Quick-and-dirty class for managing settings for a WordPress plugin.

wordpress_settings.php

<?php

/**
 * Quick-and-dirty class for managing WordPress options for a plugin.
 * Include this class in your plugin. Create an instance and use as follows:
 * 
 * Required Usage: 
 * 
 *   // Create new instance
 *   $settings = new wordpress_settings;
 * 
 *   // Configure the prefix for storing and referencing your plugin's settings
 *   $settings->prefix = "plugin_prefix_";
 * 
 *   // Menu title for settings screen.
 *   $settings->menu_title = "Name of Plugin";
 * 
 *   // Add one or more settings fields. 
 *   // Here's a full example. Only required field is `id`
 *   $settings->add_field(array(
 * 
 *     # Required. The field identifier.
 *     "id" => "field_name",  
 * 
 *     # Optional.
 *     # The title of the field. When empty, defaults to a value derived from
 *     # the `id`. Used for labeling field inputs. 
 *     "title" => "Field Title",
 * 
 *     # Optional.
 *     # Long text description describing the field. Can include HTML tags. 
 *     "description" => "What this field is used for.",
 * 
 *     # Optional.
 *     # The type of input to present to the user.
 *     # Defaults to "text", e.g., `<input type="text">`
 *     # NOTE: currently "text" is the only supported option. 
 *     "input" => "text", 
 * 
 *     # Optoinal. 
 *     # The default value for the field
 *     "default" => "",
 * 
 *   ));
 * 
 *   //
 *   // Once configured call `hook()` to integrate into WordPress.
 *   //
 *   $settings->hook();
 * 
 * 
 * Optional Configuration:
 * 
 *   // Page title for settings screen. Defaults to the menu title. 
 *   $settings->page_title = "Settings for Name of Plugin";
 * 
 *   // Width of input text fields. Defaults to "80%".
 *   $settings->input_text_width = "100%";
 * 
 * 
 */
class wordpress_settings {
	
	/**
	 * The prefix used when settings are stored in the WordPress database
	 * @var string 
	 */
	public $prefix = "";
	
	/**
	 * The title of the WordPress Dashboard settings menu item. 
	 * @var string 
	 */
	public $menu_title = "";
	
	/**
	 * The page title of the settings screen in the WordPress Dashboard. 
	 * @var string 
	 */
	public $page_title = "";
	
	/**
	 * The CSS `width` value to assign to text inputs. 
	 * @var string 
	 */
	public $input_text_width = "80%";
		
	/**
	 * Add a settings field.
	 * @param array $args
	 */
	public function add_field(array $args) {
		$field = $this->create_field($args);
		$this->_fields[$field["id"]] = $field;
	}
	
	/**
	 * Internal collection of settings fields.
	 * @var array 
	 */
	protected $_fields = array();
	
	/**
	 * Create a settings field array, ensuring defaults are populated. 
	 * @param array $args
	 * @return array
	 */
	public function create_field(array $args) {
		$defaults = array(
				"id" => "",
				"title" => "",
				"description" => "",
				"input" => "text",  // currently only "text"
				"default" => "",
		);
		$field = array_merge($defaults, $args);
		if (empty($field["title"])) {
			$field["title"] = ucwords(implode(" ", array_map("trim", preg_split('/[_-]+/', $field["id"]))));
		}
		return $field;
	}
	
	/**
	 * Check if a field exists.
	 * @param string $k The id of the field to check. 
	 * @return boolean|array FALSE when field was not found. Otherwise, returns a field array. 
	 */
	public function field_exists($k) {
		if (array_key_exists($k, $this->_fields)) {
			return $this->_fields[$k];
		} else {
			return false;
		}
	}
	
	/**
	 * Format a field id as a unique option key, for storing the field value in the WordPress database.
	 * @param string $k The field id. 
	 * @return string
	 */
	public function option_key($k) {
		if (empty($this->prefix)) {
			return $k;
		} else {
			return $this->prefix . $k;
		}
	}
	
	/**
	 * Check if the named settings field exists.
	 * @param string $k The field id.
	 * @return boolean
	 */
	function __isset($k) {
		return !!$this->field_exists($k);
	}
	
	/**
	 * Remove a settings field.
	 * @param string $k The field id.
	 */
	function __unset($k) {
		unset($this->_fields[$k]);
	}
	
	/**
	 * Get accessor for retrieving settings field values. 
	 * @param string $k The field id
	 * @return mixed NULL when the field was not found. Otherwise, the configured field value. Or the field's default value when a value has not yet been set. 
	 */
	function __get($k) {
		if ($field = $this->field_exists($k)) {
			$ok = $this->option_key($k);
			$v = get_option($ok, $field["default"]);
			return $v;
		}
		return null;
	}
	
	/**
	 * Set accessor for configuring a settings field value
	 * @param string $k The field id
	 * @param string $v The field value, as fed to `update_option`. Can contain any serializable value. 
	 */
	function __set($k, $v) {
		if ($this->field_exists($k)) {
			$ok = $this->option_key($k);
			update_option($ok, $v);
		}
	}
	
	/**
	 * Hook into WordPress.
	 * Sets up the settings form screens in WordPress Dashboard. 
	 */
	public function hook() {
		if (is_admin()) {
			add_action("admin_init", array(&$this, "settings_form_save"));
			add_action("admin_menu", array(&$this, "setup_menu"));
		}
	}
	
	/**
	 * Detect and handle form save requests. 
	 */
	public function settings_form_save() {
		$save_action = $this->prefix . "settings_form_save";
		$do_save = isset($_POST["action"]) && $_POST["action"] === $save_action;
		if ($do_save) {
			if (check_admin_referer($save_action)) {
				foreach ($_POST as $fid => $v) {
					$this->$fid = $v;
				}
				$redirect_url = $_POST["_wp_http_referer"];
				if (strpos($redirect_url, "&updated=1") === false) {
					$redirect_url .= "&updated=1";
				}
				wp_safe_redirect($redirect_url);
			} else {
				wp_die("Unable to save settings: nonce verification failed.");
			}
		}
	}
	
	/**
	 * Add settings screen to WordPress dashboard. 
	 */
	public function setup_menu() {
		add_submenu_page("options-general.php", ($this->page_title ? $this->page_title : $this->menu_title), $this->menu_title, "manage_options", "{$this->prefix}menu", array(&$this, "settings_screen"));
	}
	
	/**
	 * Output the settings screen. 
	 */
	public function settings_screen() {
		$nonce_name = "{$this->prefix}settings_form_save";
?>
<div class="wrap">
  <h2><?php echo ($this->page_title ? $this->page_title : $this->menu_title); ?></h2>
	<form method="post" action="" class="<?php echo $this->prefix; ?>_settings_form">
		<input type="hidden" name="action" value="<?php echo $nonce_name; ?>">
		<?php wp_nonce_field($nonce_name); ?>
		<table class="form-table">
		<?php
			foreach ($this->_fields as $field_id => $field) {
				$dom_id = $this->prefix . $field_id;
		?>
    <tr valign="top">
      <th scope="row">
        <label for="<?php echo $dom_id; ?>"><?php echo $field["title"]; ?></label>
      </th>
			<td>
				<input type="text" id="<?php echo $dom_id; ?>" name="<?php echo $field_id; ?>" value="<?php echo esc_attr($this->$field_id); ?>"<?php if ($this->input_text_width) { printf(' style="width: %s"', $this->input_text_width); } ?>>
				<?php if ($field["description"]) { ?>
				<p class="description"><?php echo $field["description"]; ?></p>
				<?php } ?>
			</td>
		</tr>
		<?php
			}
		?>
		</table>
    <p class="submit">
      <input type="submit" value="Save Settings" class="button-primary">
    </p>
	</form>
</div>
<?php
	}
	
}