Settings builder utility for WordPress (can be used as a mu-plugin)

example.php

<?php

add_action( 'plugins_loaded', function() {

	$settings = new zacscott\SettingsBuilder();

	$settings->page( array(
		'title'      => 'TEST ',
		'menu' => 'Test Settings',
	) );

	$settings->section( array(
		'title' => 'Test Settings',
	) );

	$settings->text( array(
		'label'  => __( 'Textual option', 'text_domain' ),
		'option' => 'text_op',
	) );

	$settings->number( array(
		'label'  => __( 'Number option', 'text_domain' ),
		'option' => 'number_op',
	) );

	$settings->bool( array(
		'label'  => __( 'Boolean option', 'text_domain' ),
		'option' => 'bool_op',
	) );

	$settings->select( array(
		'label'  => __( 'Select options', 'text_domain' ),
		'option' => 'select_op',
		'vals' => array(
		    'test1' => 'Test 1',
		    'test2' => 'Test 2',
		    'test3' => 'Test 3',
		  )
	) );

	$settings->build();

} );

settings-builder.php

<?php
/*
 * Plugin Name: Settings Builder
 * Description: Simple WP settings builder API
 * Version: 1.0
 * Author: Zachary Scott
 */

namespace zacscott;

/**
 * A single settings field in a Section.  Used internally by Section.
 *
 * @author Zachary Scott <zscott.dev@gmail.com>
 */
class Field {

	public $args = array();

	public function __construct( $args ) {
		assert( ! empty( $args ) );
		$this->args = $args;
	}

	/**
	 * Registers the settings field with WordPress.
	 * Must be called within 'admin_init' hook.
	 *
	 * @param $id The ID of the setting field.
	 * @param $page The Page object which this field belongs to.
	 */
	public function build( $id, $page ) {
		assert( ! empty( $id ) );
		assert( ! empty( $page ) );

		if ( 'hr' !== (string) $this->type ) { // dont register setting for <hr>

			// register the option setting
			register_setting(
				$page,
				$this->option,
				array( $this, 'validate' )
			);

		}

		add_settings_field(
			$this->option,
			$this->label,
			array( $this, $this->type ),
			$page,
			$id,
			array( // args to callback
			    $this->vals
			)
		);

	}

	// Validates the setting field.
	function validate( $value ) {

		$validate = $this->validate;

		if ( ! empty( $validate ) ) {

			$err = call_user_func( $validate, $value );

			// report error - if any
			if ( ! empty( $err ) ) {
				add_settings_error( $this->option, $this->option, $err );
				return get_option( $this->option ); // failed - revert to previous value
			}
		}

		return $value;

	}

	// Output <input type="checkbox"/>
	function bool() {
		assert( 'bool' === (string) $this->type );

		$val  = get_option( $this->option );
		$name = $this->option;

		echo "<label for='". esc_attr( $name ) ."'>";
		echo "<input type='checkbox' id='". esc_attr( $name ) ."' name='". esc_attr( $name ) ."' ";
		echo esc_attr( $val ? "checked='checked'" : '' );
		echo "/> \n";
		echo esc_html( $this->placeholder );
		echo '</label>';

	}

	// Output <input type="text"/>
	function text() {
		assert( 'text' === (string) $this->type );

		$val  = get_option( $this->option );
		$name = $this->option;
		$placeholder = $this->placeholder;

		echo "<input type='text' name='". esc_attr( $name ) ."' ";
		echo "value='". esc_attr( $val ) ."' ";
		echo "placeholder='". esc_attr( $placeholder ) ."'/> \n";

	}

	// Output <textarea/>
	function textarea() {
		assert( 'textarea' === $this->type );

		$val  = get_option( $this->option );
		$name = $this->option;
		$placeholder = $this->placeholder;

		echo "<textarea cols='40' rows='8' ";
		echo "name='". esc_attr( $name ) ."'";
		echo "placeholder='". esc_attr( $placeholder ) ."'";
		echo '>'. esc_html( $val ) ."</textarea> \n";

	}

	// Output <input type="number"/>
	function number() {
		assert( 'number' === (string) $this->type );

		$val  = get_option( $this->option );
		$name = $this->option;
		$placeholder = $this->placeholder;

		echo "<input type='number' ";
		echo "name='". esc_attr( $name ) ."' ";
		echo "value='". esc_attr( $val ) ."' ";
		echo "placeholder='". esc_attr( $placeholder ) ."'/> \n";

	}

	// Output <select>
	function select() {
		assert( 'select' === (string) $this->type );

		$current = (string) get_option( $this->option );
		$name    = $this->option;

		echo '<select name="'. esc_attr( $name ) .'"> ' ."\n";

		// add all available options
		foreach ( $this->vals as $key => $val ) {
			$key = esc_attr( $key );
			$val = esc_html( $val );

			// whether the current one - will be selected
			$selected = ( (string) $key === $current ) ? ' selected="selected"' : '';

			// output <option>
			echo '<option value="'. esc_attr( $key ) .'"'. esc_attr( $selected ) .'>';
			echo esc_html( $val );
			echo '</option>';
			echo "\n";

		}

		echo "</select> \n";

	}

	// Output <hr>
	function hr() {
		echo '<hr>';
	}

	// $args acessor
	function __get( $name ) {
		return isset( $this->args[ $name ] ) ? $this->args[ $name ] : '';
	}

}

/**
 * A settings section which contains zero or more Field's.
 * Used internally by Page.
 *
 * @author Zachary Scott <zscott.dev@gmail.com>
 */
class Section {

	private $args = array();
	private $fields = array(); // all fields in the section
	public $id; // unique ID of the section

	public function __construct( $args ) {

		assert( ! empty( $args ) );
		$this->args = $args;

		// Generate random ID for the section
		$this->id = uniqid( '_', true );

	}

	/**
	 * Add the given field to the section.
	 *
	 * @param Field $field The field object to add.
	 */
	public function add( $field ) {
		assert( ! empty( $field ) );
		$this->fields[] = $field;
	}

	/**
	 * Registers the settings section and its fields with WordPress.
	 * Must be called within 'admin_init' hook.
	 *
	 * @param $page The page to which the section belongs
	 */
	public function build( $page ) {
		assert( ! empty( $page ) );

		$subtext = $this->subtext;

		// add the settings section
		add_settings_section(
			$this->id,
			$this->title,
			array( $this, 'subtext' ),
			$page
		);

		// add all section settings
		foreach ( $this->fields as $field ) {
			$field->build( $this->id, $page );
		}

	}

	// Spits out the subtext for the section
	function subtext() {
		echo '<p>'. esc_html( $this->subtext ) .'</p>';
	}

	// $args acessor
	function __get( $name ) {
		return isset( $this->args[ $name ] ) ? $this->args[ $name ] : '';
	}

}

/**
 * A settings page - which contains one or more Section's.  Each Section
 * encapsultes zero or more `Field`s.  Each field represents a WordPress option
 * which can be changed.
 *
 * Used internally by `SettingsBuilder`.
 *
 * @author Zachary Scott <zscott.dev@gmail.com>
 */
class Page {

	// count of all page instances for menu slug
	private static $count = 1;

	private $args = array();
	private $slug;
	private $sections; // list of settings sections on the page

	public function __construct( $args ) {
		assert( ! empty( $args ) );

		$default_args = array(
			'title' => '',
			'menu'  => '',
			'cap'   => 'manage_options',
		);
		$this->args = array_merge( $default_args, $args );

		$this->slug = plugin_basename( dirname( __FILE__ ) ) .'-settings-'. Page::$count++;

	}

	/**
	 * Creates a new section in which to place subsequent settings.
	 *
	 * @param $title - The title of the section to display to the user.
	 */
	public function section( $args ) {
		assert( ! empty( $args ) );
		$this->sections[] = new Section( $args );
	}

	/**
	 * Creates a boolean setting field (checkbox).
	 *
	 * @param string $label The label to display on the page
	 * @param string $option The option name (wp option API)
	 * @param string $placeholder The placeholder text when no option is selected
	 * @param string $validate Validation callback
	 */
	public function bool( $args ) {
		assert( ! empty( $this->sections ) );
		assert( ! empty( $args ) );

		$default_args = array(
			'type' => 'bool',
		);
		$args = array_merge( $default_args, $args );

		$this->add_field( new Field( $args ) );

	}

	/**
	 * Creates a textual setting field (textbox).
	 *
	 * @param string $label The label to display on the page
	 * @param string $option The option name (wp option API)
	 * @param string $placeholder The placeholder text when no option is selected
	 * @param string $validate Validation callback
	 */
	public function text( $args ) {
		assert( ! empty( $this->sections ) );
		assert( ! empty( $args ) );

		$default_args = array(
			'type' => 'text',
		);
		$args = array_merge( $default_args, $args );

		$this->add_field( new Field( $args ) );

	}

	/**
	 * Creates a multi-line textarea setting field (textarea).
	 *
	 * @param string $label The label to display on the page
	 * @param string $option The option name (wp option API)
	 * @param string $placeholder The placeholder text when no option is selected
	 * @param string $validate Validation callback
	 */
	public function textarea( $args ) {
		assert( ! empty( $this->sections ) );
		assert( ! empty( $args ) );

		$default_args = array(
			'type' => 'textarea',
		);
		$args = array_merge( $default_args, $args );

		$this->add_field( new Field( $args ) );

	}


	/**
	 * Creates a number setting field.
	 *
	 * @param string $label The label to display on the page
	 * @param string $option The option name (wp option API)
	 * @param string $placeholder The placeholder text when no option is selected
	 * @param string $validate Validation callback
	 */
	public function number( $args ) {
		assert( ! empty( $this->sections ) );
		assert( ! empty( $args ) );

		$default_args = array(
			'type' => 'number',
		);
		$args = array_merge( $default_args, $args );

		$this->add_field( new Field( $args ) );

	}


	/**
	 * Creates a list of options (combobox).
	 *
	 * @param string $label The label to display on the page
	 * @param string $option The option name (wp option API)
	 * @param string $vals The list of available options
	 * @param string $validate Validation callback
	 */
	public function select( $args ) {
		assert( ! empty( $this->sections ) );
		assert( ! empty( $args ) );

		$default_args = array(
			'type' => 'select',
		);
		$args = array_merge( $default_args, $args );

		$this->add_field( new Field( $args ) );

	}

	/** Creates a <hr>. */
	public function hr() {

		$args = array(
			'type'   => 'hr',
			'option' => mt_rand(),
		);

		$this->add_field( new Field( $args ) );

	}

	// Adds the given field to the page
	private function add_field( $field ) {
		assert( ! empty( $field ) );

		$end = sizeof( $this->sections );
		$this->sections[ $end - 1 ]->add( $field );

	}

	/**
	 * Registers the options page with WordPress.
	 * Must be called within 'admin_init' hook.
	 */
	public function build() {

		// register the page w/ wordpress
		add_action( 'admin_menu', array( $this, 'register_settings_page' ), 999999999 );

		// register the settigns sections with wordpress
		add_action( 'admin_init', array( $this, 'register_settings' ), 999999999 );

	}

	// Registers the settings page w/ WP
	function register_settings_page() {

		add_options_page(
			$this->title,
			$this->menu,
			$this->cap,
			$this->slug,
			array( $this, 'render' )
		);

	}

	// Registers the page settings w/ WP
	public function register_settings() {

		// build each settings section
		foreach ( $this->sections as $section ) {
			$section->build( $this->slug );
		}

	}

	// Renders the options page
	public function render() {

		echo '<h1>' . esc_html( $this->title ) . '</h1> <br>';

		// render the options form
		echo '<form method="post" action="options.php">';

		settings_fields( $this->slug );
		do_settings_sections( $this->slug );

		submit_button();

		echo '</form>';

	}

	// $args acessor
	function __get( $name ) {
		return isset( $this->args[ $name ] ) ? $this->args[ $name ] : '';
	}

}

/**
 * Helps build a WordPress settings section with a much nicer interface.  Yeah
 * WordPress's Settings API sucks!
 *
 * Can be used like so:
 *
 *    $settings = new SettingsBuilder();
 *
 *    $settings->page( array(
 *    	'title' => 'My Page Title',
 *    	'menu' => 'Test Settings'
 *    ) );
 *
 *    $settings->section( array(
 *    	'title' => 'Test Settings'
 *    ) );
 *
 *    $settings->text( array(
 *    	'label'  => __( 'Textual option', 'text_domain' ),
 *    	'option' => 'text_op'
 *    ) );
 *
 *    $settings->bool( array(
 *    	'label'  => __( 'Boolean option', 'text_domain' ),
 *    	'option' => 'bool_op'
 *    ) );
 *
 *    $settings->select( array(
 *    	'label'  => __( 'Select options', 'text_domain' ),
 *    	'option' => 'select_op',
 *    	'vals' => array(
 *        'test1' => 'Test 1',
 *        'test2' => 'Test 2',
 *        'test3' => 'Test 3'
 *      )
 *    ) );
 *
 *    // etc ...
 *
 *    $settings->build();
 *
 * @author Zachary Scott <zscott.dev@gmail.com>
 */
class SettingsBuilder {

	// list of settings pages
	private $pages;

	/**
	 * Creates a settings page on which subsequent sections will be placed.
	 *
	 * @param string $title The title of the settings page.
	 * @param string $menu The menu title
	 * @param string $cap The required capability for page to be visible
	 * (default 'manage_options').
	 */
	public function page( $args ) {
		assert( ! empty( $args ) );

		// add the page to the list
		$this->pages[] = new Page( $args );

	}

	/**
	 * Creates a new section in which to place subsequent settings.
	 *
	 * @param string $title The title of the section to display to the user.
	 * @param string $page The theme page to which the section belongs.
	 */
	public function section( $args ) {
		assert( ! empty( $args ) );

		$end = sizeof( $this->pages );
		$this->pages[ $end - 1 ]->section( $args );

	}

	/**
	 * Creates a boolean setting field (checkbox).
	 *
	 * @param string $label The label to display on the page
	 * @param string $option The option name (wp option API)
	 * @param string $placeholder The placeholder text when no option is selected
	 * @param string $validate Validation callback
	 */
	public function bool( $args ) {
		assert( ! empty( $args ) );

		$end = sizeof( $this->pages );
		$this->pages[ $end - 1 ]->bool( $args );

	}

	/**
	 * Creates a textual setting field (textbox).
	 *
	 * @param string $label The label to display on the page
	 * @param string $option The option name (wp option API)
	 * @param string $placeholder The placeholder text when no option is selected
	 * @param string $validate Validation callback
	 */
	public function text( $args ) {
		assert( ! empty( $args ) );

		$end = sizeof( $this->pages );
		$this->pages[ $end - 1 ]->text( $args );

	}

	/**
	 * Creates a multi-line textarea setting field (textarea).
	 *
	 * @param string $label The label to display on the page
	 * @param string $option The option name (wp option API)
	 * @param string $placeholder The placeholder text when no option is selected
	 * @param string $validate Validation callback
	 */
	public function textarea( $args ) {
		assert( ! empty( $args ) );

		$end = sizeof( $this->pages );
		$this->pages[ $end - 1 ]->textarea( $args );

	}

	/**
	 * Creates a number setting field (textbox).
	 *
	 * @param string $label The label to display on the page
	 * @param string $option The option name (wp option API)
	 * @param string $placeholder The placeholder text when no option is selected
	 * @param string $validate Validation callback
	 */
	public function number( $args ) {
		assert( ! empty( $args ) );

		$end = sizeof( $this->pages );
		$this->pages[ $end - 1 ]->number( $args );

	}

	/**
	 * Creates a list of options (combobox).
	 *
	 * @param string $label The label to display on the page
	 * @param string $option The option name (wp option API)
	 * @param string $vals The list of available options
	 * @param string $validate Validation callback
	 */
	public function select( $args ) {
		assert( ! empty( $args ) );

		$end = sizeof( $this->pages );
		$this->pages[ $end - 1 ]->select( $args );

	}

	/** Creates a <hr> */
	public function hr() {

		$end = sizeof( $this->pages );
		$this->pages[ $end - 1 ]->hr( array() );

	}

	/** Registers the settings pages, sections and fields with wordpress. */
	public function build() {

		// build each settings page
		foreach ( $this->pages as $page ) {
			$page->build();
		}

	}

}

/** @file SettingsBuilder.php - Simple WP settings builder API
 * Copyright (c) 2014, 2015 <zscott.dev@gmail.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */