php base64字符串转二进制流

function base64_to_blob($base64Str){
    if($index = strpos($base64Str,'base64,',0)){
        $blobStr = substr($base64Str,$index+7);
        $typestr = substr($base64Str,0,$index);
        preg_match("/^data:(.*);$/",$typestr,$arr);
        return ['blob'=>base64_decode($blobStr),'type'=>$arr[1]];
    }
    return false;
}