A base for a WordPress plugin settings page, using the Settings API #add_options_page #add_action #admin_init #register_setting #add_settings_section

plugin-settings.php

<?php
# http://kovshenin.com/2012/the-wordpress-settings-api/
# http://codex.wordpress.org/Settings_API

add_action( 'admin_menu', 'my_admin_menu' );
function my_admin_menu() {
    add_options_page( __('My Plugin Options', 'textdomain' ), __('My Plugin Options', 'textdomain' ), 'manage_options', 'my-plugin', 'my_options_page' );
}
add_action( 'admin_init', 'my_admin_init' );

function my_admin_init() {
  
  /* 
	 * http://codex.wordpress.org/Function_Reference/register_setting
	 * register_setting( $option_group, $option_name, $sanitize_callback );
	 * The second argument ($option_name) is the option name. It’s the one we use with functions like get_option() and update_option()
	 * */
  	# With input validation:
  	# register_setting( 'my-settings-group', 'my-plugin-settings', 'my_settings_validate_and_sanitize' );    
  	register_setting( 'my-settings-group', 'my-plugin-settings' );
	
  	/* 
	 * http://codex.wordpress.org/Function_Reference/add_settings_section
	 * add_settings_section( $id, $title, $callback, $page ); 
	 * */	 
  	add_settings_section( 'section-1', __( 'Section One', 'textdomain' ), 'section_1_callback', 'my-plugin' );
	add_settings_section( 'section-2', __( 'Section Two', 'textdomain' ), 'section_2_callback', 'my-plugin' );
	
	/* 
	 * http://codex.wordpress.org/Function_Reference/add_settings_field
	 * add_settings_field( $id, $title, $callback, $page, $section, $args );
	 * */
  	add_settings_field( 'field-1-1', __( 'Field One', 'textdomain' ), 'field_1_1_callback', 'my-plugin', 'section-1' );
	add_settings_field( 'field-1-2', __( 'Field Two', 'textdomain' ), 'field_1_2_callback', 'my-plugin', 'section-1' );
	
	add_settings_field( 'field-2-1', __( 'Field One', 'textdomain' ), 'field_2_1_callback', 'my-plugin', 'section-2' );
	add_settings_field( 'field-2-2', __( 'Field Two', 'textdomain' ), 'field_2_2_callback', 'my-plugin', 'section-2' );
	
}
/* 
 * THE ACTUAL PAGE 
 * */
function my_options_page() {
?>
  <div class="wrap">
      <h2><?php _e('My Plugin Options', 'textdomain'); ?></h2>
      <form action="options.php" method="POST">
        <?php settings_fields('my-settings-group'); ?>
        <?php do_settings_sections('my-plugin'); ?>
        <?php submit_button(); ?>
      </form>
  </div>
<?php }
/*
* THE SECTIONS
* Hint: You can omit using add_settings_field() and instead
* directly put the input fields into the sections.
* */
function section_1_callback() {
	_e( 'Some help text regarding Section One goes here.', 'textdomain' );
}
function section_2_callback() {
	_e( 'Some help text regarding Section Two goes here.', 'textdomain' );
}
/*
* THE FIELDS
* */
function field_1_1_callback() {
	
	$settings = (array) get_option( 'my-plugin-settings' );
	$field = "field_1_1";
	$value = esc_attr( $settings[$field] );
	
	echo "<input type='text' name='my-plugin-settings[$field]' value='$value' />";
}
function field_1_2_callback() {
	
	$settings = (array) get_option( 'my-plugin-settings' );
	$field = "field_1_2";
	$value = esc_attr( $settings[$field] );
	
	echo "<input type='text' name='my-plugin-settings[$field]' value='$value' />";
}
function field_2_1_callback() {
	
	$settings = (array) get_option( 'my-plugin-settings' );
	$field = "field_2_1";
	$value = esc_attr( $settings[$field] );
	
	echo "<input type='text' name='my-plugin-settings[$field]' value='$value' />";
}
function field_2_2_callback() {
	
	$settings = (array) get_option( 'my-plugin-settings' );
	$field = "field_2_2";
	$value = esc_attr( $settings[$field] );
	
	echo "<input type='text' name='my-plugin-settings[$field]' value='$value' />";
}
/*
* INPUT VALIDATION:
* */
function my_settings_validate_and_sanitize( $input ) {

	$settings = (array) get_option( 'my-plugin-settings' );
	
	if ( $some_condition == $input['field_1_1'] ) {
		$output['field_1_1'] = $input['field_1_1'];
	} else {
		add_settings_error( 'my-plugin-settings', 'invalid-field_1_1', 'You have entered an invalid value into Field One.' );
	}
	
	if ( $some_condition == $input['field_1_2'] ) {
		$output['field_1_2'] = $input['field_1_2'];
	} else {
		add_settings_error( 'my-plugin-settings', 'invalid-field_1_2', 'You have entered an invalid value into Field One.' );
	}
	
	// and so on for each field
	
	return $output;
}

Where do i put this

Where do i put this

For example template functions file functions.php