php中使用gd库实现下载网页中所有图片

<"Content-type:text/html ; charset=utf-8");
if (!empty($_POST['submit'])){
 $url = $_POST['url'];
 //为了获取相对路径的图片所做的操作
 $url_fields = parse_url($url);
 $main_url = $url_fields['host'];
 $base_url = substr($url,0,strrpos($url, '/')+1);
 //获取网页内容
 //设置代理服务器
 $opts = array('http'=>array('request_fulluri'=>true));
 $context = stream_context_create($opts);
 $content = file_get_contents($url,false,$context);
 //匹配img标签,将所有匹配字符串保存到数组$matches
 $reg = "/<img.*"(.*".*";
 preg_match_all($reg, $content, $matches);
 $count = count($matches[0]);
 for ($i=0; $i<$count; $i++){
 /*将所有图片的url转换为小写
  *$matches[1][$i] = strtolower($matches[1][$i]);
 */
 //如果图片为相对路径就转化为全路径
 if (!strpos('a'.$matches[1][$i], 'http')){
  //因为'/'是第0个位置
  if (strpos('a'.$matches[1][$i], '/')){
  $matches[1][$i] = 'http://'.$main_url.$matches[1][$i];
  }else{
  $matches[1][$i] = $base_url.$matches[1][$i];
  }
 }
 }
 //过滤重复的图片
 $img_arr = array_unique($matches[1]);
 //实例化图片下载类
 $getImg = new DownImage();
 $url_count = count($img_arr);
 for ($i=0; $i<$url_count; $i++){
 $getImg->source = $img_arr[$i];
 $getImg->save_address = './pic/';
 $file = $getImg->download();
 }
 echo "下载完成！哈哈，简单吧！";
}
class DownImage{
 public $source;//远程图片URL
 public $save_address;//保存本地地址
 public $set_extension; //设置图片扩展名
 public $quality; //图片的质量（0~100,100最佳，默认75左右）
 //下载方法（选用GD库图片下载）
 public function download(){
 //获取远程图片信息
 $info = @getimagesize($this->source);
 //获取图片扩展名
 $mime = $info['mime'];
 $type = substr(strrchr($mime, '/'), 1);
 //不同的图片类型选择不同的图片生成和保存函数
 switch($type){
  case 'jpeg':
  $img_create_func = 'imagecreatefromjpeg';
  $img_save_func = 'imagejpeg';
  $new_img_ext = 'jpg';
  $image_quality = isset($this->quality) ".");
  $strlen = strlen($ext);
  $newname = basename(substr($this->source,0,-$strlen)).'.'.$new_img_ext;
 }else{
  $newname = basename($this->source);
 }
 
 //生成本地文件路径
 $save_address = $this->save_address.$newname;
 $img = @$img_create_func($this->source);
 if (isset($image_quality)){
  $save_img = @$img_save_func($img,$save_address,$image_quality);
 }else{
  $save_img = @$img_save_func($img,$save_address);
 }
 return $save_img; 
 }
}
"POST" action="">
远程url地址：<input type="text" name="url" size=30 />
<input type="submit" name="submit" value="下载该页面所有图片" />
</form>