php接收ios/android上传图片

//base64二进制图片流
$file_name = base64_decode($_POST['images']);

//验证头像格式
$bin = substr($file_name,0,2);
$strInfo = @unpack("C2chars", $bin);
$typeCode = intval($strInfo['chars1'].$strInfo['chars2']);
$fileType = '';
switch ($typeCode)
{
case 7790:
$fileType = 'exe';
break;
case 7784:
$fileType = 'midi';
break;
case 8297:
$fileType = 'rar';
break;
case 255216:
$fileType = 'jpg';
break;
case 7173:
$fileType = 'gif';
break;
case 6677:
$fileType = 'bmp';
break;
case 13780:
$fileType = 'png';
break;
default:
echo 'unknown';
}
if(!empty($file_name)||!empty($user_id)){

$upfile='images/face/'.'face_'.'123'.'.jpg';
$file=$_SERVER['DOCUMENT_ROOT'].'/images/face/'.'face_'.'123'.'.jpg';
$m=fopen($file,"w");//当参数为"w"时是将内容覆盖写入文件，而当参数为"a"时是将内容追加写入。
//$content=$result['keyword']."\t\t\n";
fwrite($m,$file_name);
fclose($m);
json(200,'success',1);
}else{
json(401,'error',0);
}