<?php
function my_theme_customizer() {
	//add panel
	$wp_customize->add_panel('my_option_panel', array(
		'priority' => 10,
		'title' => 'my panel'
	));
}
add_action('customize_register', 'my_theme_customizer');



//sanitize
//select box
function sanitize_choices($input, $setting) {
	global $wp_customize;
	$control = $wp_customize->get_control($setting->id);
	if(array_key_exists($input, $control->choices)) {
		return $input;
	} else {
		return $setting->default;
	}
}

//check box
function sanitize_checkbox($input) {
	if($input == true) {
		return true;
	} else {
		return false;
	}
}

//text area
if(class_exists('WP_Customize_Control')) : class Customize_Textarea_Control extends WP_Customize_Control {
	public $type = 'textarea';
	public function render_content() {
?>
<label>
<span class="customize-control-title"><?php echo esc_html($this->label); ?></span>
<textarea rows="6" style="width: 100%" <?php $this->link(); ?>><?php echo esc_textarea($this->value()); ?></textarea>
</label>
<?php
	}
}
endif;