// 記事内の画像を取ってくる
function catch_that_image() {
    global $post, $posts;
    $first_img = '';
    ob_start();
    ob_end_clean();
    $output = preg_match_all('/<img.+src=[\'"]([^\'"]+)[\'"].*>/i', $post->post_content, $matches);
    $first_img = $matches [1] [0];
 
    if(empty($first_img)){ //Defines a default image
        $first_img = "/images/default.jpg";
    }
return $first_img;
}