Yeadh

<?php
/** Image PlaceHolder for PHP.
 * Usage : iph.php?<WIDTH>x<HEIGHT>/<COLOR>
 * Ex : iph.php?800x600/FF00FF
 * Author : Léo Peltier
 * LICENSE : WTFPL
 * */

return main();

Yeadh

$wp_customize->add_setting( 'themeslug_select_setting_id', array(
  'capability' => 'edit_theme_options',
  'sanitize_callback' => 'themeslug_sanitize_select',
  'default' => 'value1',
) );

$wp_customize->add_control( 'themeslug_select_setting_id', array(
  'type' => 'select',
  'section' => 'custom_section', // Add a default or your own section
  'label' => __( 'Custom Select Option' ),

Yeadh

$wp_customize->add_setting( 'themecheck_checkbox_setting_id', array(
  'capability' => 'edit_theme_options',
  'sanitize_callback' => 'themeslug_sanitize_checkbox',
) );

$wp_customize->add_control( 'themeslug_checkbox_setting_id', array(
  'type' => 'checkbox',
  'section' => 'custom_section', // Add a default or your own section
  'label' => __( 'Custom Checkbox' ),
  'description' => __( 'This is a custom checkbox input.' ),

Yeadh

$wp_customize->add_setting( 'themeslug_textarea_setting_id', array(
  'capability' => 'edit_theme_options',
  'default' => 'Lorem Ipsum Dolor Sit amet',
  'sanitize_callback' => 'sanitize_text_field',
) );

$wp_customize->add_control( 'themeslug_textarea_setting_id', array(
  'type' => 'textarea',
  'section' => 'custom_section', // // Add a default or your own section
  'label' => __( 'Custom Text Area' ),

Yeadh

/**
 * WP_Customize_Manager->add_setting(); // adds a new setting to the database
 * WP_Customize_Manager->add_section(); // adds a new section (i.e. category/group) to the Theme Customizer page
 * WP_Customize_Manager->add_control(); // creates an HTML control that admins can use to change settings.
 * WP_Customize_Manager->get_setting(); // can be used to fetch any existing setting, in the event you need to modify something
 */


add_action( 'customize_register', 'my_customize_register' );
function my_customize_register( $wp_customize ) {