您还可以使用WordPress本身提供的正则表达式get_shortcode_regex:

function wpse250308_get_questions() {
    global $post;
    if ( preg_match_all(get_shortcode_regex(\'question\'), $post->post_content, $questions ) ) {
        $questions = array_key_exists( 1 , $questions) ? $questions[1] : array();
        // $questions will contain the array of the question shortcodes
        // but also, get_shortcode_regex returns a regex that provides some useful capture groups:
        // the get_shortcode_regex from WP provides the matches:
        // 1 – An extra [ to allow for escaping shortcodes with double [[]] 
        // 2 – The shortcode name 
        // 3 – The shortcode argument list 
        // 4 – The self closing / 
        // 5 – The content of a shortcode when it wraps some content. 
        // 6 – An extra ] to allow for escaping shortcodes with double [[]]
        //Do your stuff
    }
}