使用javascript上传图片

Question

I'm stuck!! :( I want to upload image file with a title and a caption, I want to use javascript for validation of title caption and a file choosen.

My html goes here:

<input type="text" name="title2" id="title2" value="title" /><br />

<textarea cols="50" rows="10" name="caption" >caption goes here...</textarea><br />
<input type="file" name="photo" id="photo" /><br />
<button id="submit_info" onclick="photowcap()" >post</button><br />

and my javascript here:

function photowcap()
{

var title = document.getElementsByName("title2")[0].value;
var photo = document.getElementsByName("photo")[0].value;
var captions = document.getElementsByName("caption")[0].value;
var caption = encodeURIComponent(captions)

var xmlhttp;
if(title == "" || title == " " || title == "title")
{
    document.getElementsByName("title2")[0].focus();
    document.getElementsByName("title2")[0].value="";
    return;
}
else if(captions == "" || captions == " " || captions == "caption goes here..."){
    document.getElementsByName("caption")[0].focus();
    document.getElementsByName("caption")[0].value="";
    return;
}
else if(photo == ""){
    alert("please choose image");
}
else{
if (window.XMLHttpRequest)
{
    xmlhttp=new XMLHttpRequest();
}
else
{
    xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function()
    {
        if (xmlhttp.readyState==4 && xmlhttp.status==200)
        {
            alert("Success!!!");
        }
    }
xmlhttp.open("GET","photowcap.php?    title="+title+"&caption="+caption+"&photo="+photo,true);
    xmlhttp.send();}

}

And for saving it using php:

<?php

include("admin_conn.php");

$title = $_GET["title"];
$caption = $_GET["caption"];
$photo = $_GET["photo"];
$time=time();
$date = (date("D F d Y",$time));

$query_photowcap = "INSERT INTO school_updates(title, photo, caption, date, time)     VALUES('$title','$photo','$caption','$date','$time')";
mysql_query($query_photowcap);

?>

it only save for the file path as "C:fakepath/filename...." because I dont have any idea on how to get filename using javascript, and finally I have this code for saving the actual image into the folder but I dont really get where I should place it: THANKS IN ADVANCE :)

<?php

error_reporting(0);
$max_file_size = 200 * 1024; #200kb
if (($_FILES["photo"]["type"] == "image/gif")
  || ($_FILES["photo"]["type"] == "image/jpeg")
  || ($_FILES["photo"]["type"] == "image/png" )
  && ($_FILES["photo"]["size"] < $max_file_size))
  {
  $path = 'images/' . uniqid();
  move_uploaded_file($_FILES["photo"]["tmp_name"],
  $path.$_FILES["photo"]["name"]);

  }
else
  {
  echo "Files must be either JPEG, GIF, or PNG and less than 200 kb";
  }

?>

Answer 1

In order to access files with the $_FILES superglobal they need to be sent with a multipart/form-data content-type header and appropriate attributes. Unfortunately you cannot do this with xhr 's send method manually because sending a string will be automatically converted to UTF-8 . Fortunately though you can still send binary data such as a file from javascript's window.File .

This is not supported in older browsers. The code would look like

var file = document.getElementById('photo').files[0];

...

xhr.send(file);

And then on the server side you will need to access the input buffer directly in order to grab a hold of this file

$file = file_get_contents('php://input');

If you insist on using $_FILES you could use the FormData object in javascript. The reason I left this as a second option is because I've heard about greater support issues and I personally avoid using it for now.

var formData = new FormData(document.getElementById('theForm'));
...
xhr.send(formData);

EDIT 2016

It has been some time now since I posted this answer and now the FormData object is widely supported, if you are looking to upload files along with other data you may look into that.

Answer 2

You are trying to upload an image with ajax... short answer... normally you can't. You need a multipart/form-data to upload, making ajax upload a pain.

An easy work around would be to validate the form with js, then normally submit it. Like here: Ajax Upload image - well... ignore the title, is misleading.