select2：在编辑页面上获取所选选项

我在WordPress插件中使用select2 . 基本目的是选择多个值 . 我可以选择多个值并将它们保存在数据库中 . 问题出在编辑页面上 . 它不显示所选选项 . 但在视图源模式中，所选选项具有selected属性 .

<select name="course_info_meta[campus_id][]" id="campus_id" 
class="regular-text select2-hidden-accessible" multiple="" tabindex="-1" aria-hidden="true">
  <optgroup label="Multan College of Science">
  <option value="16"> Johar Campus </option>
  <option value="11" selected="selected"> MCH Boys Branch </option>
  <option value="13" selected="selected"> MCH Girls Branch </option>
  </optgroup>
  <optgroup></optgroup>
  <optgroup label="Jalal Pur Public School">
  <option value="14"> Boys Campus </option>
  <option value="15" selected="selected"> JPPS Shuja Abad Campus </option>
  </optgroup>
  <optgroup> </optgroup>
</select>

jQuery就在这里

jQuery(function($) {
// Select2 dropdown for campuses
    $('#campus_id').select2({
    placeholder: 'Select a Campus',             
    'multiple': true,
    closeOnSelect: false,
        });
   });

PHP代码

public function getAllCampusesList() {

        $results = $this->getAllCampusesData();


         foreach ($results as $key => $school) {

            $school_name = $this->getSchoolNameById($key);

             echo "<optgroup label='".$school_name."'>";

             foreach ($school as $campus){

                 echo "<option value='".$campus['id']."' ".$this->selected_campus($campus['id'])."> ".$campus['name']." </option>";

             } //level_2

             echo "<optgroup>";

         } //level_1

}   

 private function getAllCampusesData() {
    $transient = PMS_Management::PLUGIN_SLUG . '_campus_list';
    //delete_transient($transient);
    if ( false === ( $ret = get_transient( $transient ) ) ) {
        global $wpdb;
        $query = "SELECT id,slug FROM `{$wpdb->pms_schools}`";
        $results = $wpdb->get_results($query,ARRAY_A);
        $ret = array();
        if ( !empty( $results ) ):

            foreach ( $results as $row ):
                $slug = PMS_Management::PLUGIN_SLUG . '_' . $row['slug'];
                $args = array(
                        'orderby'       => 'date', 
                        'order'         => 'ASC',
                        'hide_empty'    => false, 
                        'fields'        => 'all', 
                        'hierarchical'  => false, 
                    );
                $terms = get_terms( $slug, $args );

                if( !is_wp_error( $terms ) && is_array( $terms ) ):
                    foreach ( $terms as $term ) {
                        $semester = array (
                            'id' => $term->term_id,
                            'name' => $term->name,
                            'slug' => $term->slug,
                        );
                        $ret[ $row['id'] ][ $term->term_id ] = $semester;

                    }
                endif;
            endforeach;

            set_transient( $transient, $ret, WEEK_IN_SECONDS );

            $transient_keys = get_option( 'my_transient_keys', array() );
            if( !array_key_exists($transient, $transient_keys) ) {
                $transient_keys[] = $transient;
                update_option( 'my_transient_keys', $transient_keys );
            }

        endif;

    }
   //echo "<pre>"; print_r($ret); echo '</pre>';        
    return $ret;
}//end of 



/* clone function for WordPress selected()
    ** It checkd either the option was selected or not
    */
    public function selected_campus($id){

    global $post;

    $get_ids = get_post_meta(get_the_ID(), '_campus_id', true);

    $ids = json_decode($get_ids, true);

    if (in_array($id, $ids)){
            $selected = 'selected="selected"';
        }
        return $selected;
    }//