xhr send base64 string and decode it in the server to a file

I am trying to to send a base64 encoded img to server,the javascript looks like

var xhr=new XMLHttpRequest()
var reader=new FileReader()
reader.onloadend=function(e){
xhr.onload=fu开发者_如何学Gonction(e){
alert(xhr.responseText)
}
xhr.open("POST","upload.php");
        xhr.setRequestHeader("Cache-Control", "no-cache");
        xhr.setRequestHeader("X-Requested-With", "XMLHttpRequest");
        //xhr.setRequestHeader("X-File-Name", file.name);
        //xhr.setRequestHeader("X-File-Type",file.type)
xhr.send(e.target.result)
}
reader.readAsDataURL(file)
},false)

In php,looks like this:

echo "some response Text";
$postdata = file_get_contents("php://input");
file_put_contents('MyFile.jpg', base64_decode($postdata));

And,eventually,the server gets a file exactly as big as the sent file,However,it can't be opened

Some one get some ideas?Thanks a lot!

reader.readAsDataURL(file)

A data URL is NOT the same as a base64 version of the file. You get extra garbage in it. It looks like this:

data:[<MIME-type>][;charset=<encoding>][;base64],<data>

See Wikipedia.

Try doing a simple regex on it:

var data = dataURL.match(/,(.*)$/)[1];

Or, in your code,

xhr.send(e.target.result.match(/,(.*)$/)[1]);