Customizer API – Class doesn’t exist error

I’m not sure if there are different approaches for this, but this is a pattern I’ve implemented successfully in several places.

In my approach, I am including the “add_control” inside the function that contains the custom class. The $wp_customize object gets passed in to the main function.

Also, I’m not sure why you are trying to include class-wp-customize-control.php.

Here’s my guess for what you need, assuming you’ve created the “bedakb_adsense” section elsewhere. Just put the following in a php file and call it from your functions.php

<?php

function bedakb_gamer_customcontrols($wp_customize) {

    class Custom_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="5" style="width:100%;" <?php $this->link(); ?>><?php echo esc_textarea( $this->value() ); ?></textarea>
            </label>
            <?php
        }
    }

    $wp_customize->add_setting( 'bedakb_ad728', array(
        'capability'  => 'edit_theme_options'
    ) );

    $wp_customize->add_control( new Custom_Textarea_Control($wp_customize, 'bedakb_ad728', array(
        'label'        => __('Adsense 728x90', 'bedakb_gamer'),
        'section'    => 'bedakb_adsense',
        'priority'    => 10,
    )));
}

add_action('customize_register', 'bedakb_gamer_customcontrols', 99);