replace img src attributes in a html string

replace_img_src_callback.php

<?php
/**
 * Created by PhpStorm.
 * User: shellus
 * Date: 2017-08-27
 * Time: 20:56
 */

/**
 * replace img src attributes in a html string
 * @param $html
 * @param $callback
 * @return string
 */
function replace_img_src_callback($html, $callback)
{
    return preg_replace_callback("/(<img.*?>)/", function ($matches) use ($callback) {
        $imgHtml = $matches[0];
        return preg_replace_callback("/src=[\"'](.*?)[\"']/", function ($matches) use ($callback) {
            $src = $matches[1];
            $src = $callback($src);
            return "src=\"$src\"";
        }, $imgHtml);
    }, $html);
}


$str = 'foo<img src="https://www.google.com/images/branding/product/ico/googleg_lodp.ico">';

var_dump(replace_img_src_callback($str, function($src){
    // note a empty string
    // if($src == "") return "";


    // download the $src to localhost
    // return localhost url

    return "http://xxx.xxx/xxx.xxx";
}));