$str = '这是一段包含图片链接的字符串，其中包括<img src="https://example.com/image1.jpg">和<img src=\'https://example.com/image2.jpg\'>。';
preg_match_all('/<img\s+src=(["\'])(.*?)\1/', $str, $matches);
$imageLinks = $matches[2];
foreach ($imageLinks as $link) { echo $link . "\n"; }
