上传原理很简单就是利用表单的打开方式为iframe的name名，这样就可以在当前页面的iframe打来了，实现文件上传，再利用js返回上传结果。
form target .在 action 属性中规定的页面会在新窗口中打开。如果是iframe，则在此iframe中打开。
phpAjaxUpload.php
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>无标题文档</title> <script type="text/javascript"> function startUpload() { document.getElementById('processing').innerHTML="正在上传中"; } function stopUpload(result) { var msg; switch(result) { case 0: msg="上传成功"; break; case 1: msg='文件大小超过限制'; break; case 2: msg='只能上传图片文件'; break; case 3: msg='move_uploaded_file失败'; break; case 4: msg="其他错误"; break; default: break; } document.getElementById('processing').innerHTML=msg; alert(msg); } </script> </head> <body> <div id="processing">结果信息</div> <form action="phpAjaxUpload2.php" method="post" enctype="multipart/form-data" target="uploadFrame" onsubmit="startUpload()"> <label for="myFile">上传文件</label> <input type="hidden" name="MAX_FILE_SIZE" value="1024000" /><input type="file" name="myFile" id="myFile" /> <input type="submit" name="submit" value="上传" /> </form> <iframe name="uploadFrame" style="0;height:0; border:0;"></iframe> </body> </html>
上面的iframe中设置width，height为0，还有一点border为0，否则还是有一点边框。注意
MAX_FILE_SIZE要仔细设定，如果文件大小大于它，那么php端$_FILES['image']['size']就会为0.
phpAjaxUpload2.php
hello <?php $result; if(isset($_POST['submit'])) { $dir='asaph/'; $maxSize=1*pow(2,20); $fileTypes=array('jpg','png','gif','bmp'); $myFileType=substr($_FILES['myFile']['name'],strpos($_FILES['myFile']['name'],'.')+1); if($_FILES['myFile']['size']>$maxSize) { $result=1; } else if(!in_array($myFileType,$fileTypes)) { $result=2; } else if(is_uploaded_file($_FILES['myFile']['tmp_name'])) { $dest=$dir.$_FILES['myFile']['name']; if( @move_uploaded_file($_FILES['myFile']['tmp_name'],$dest)) { $result=0; } else { $result=3; } } else { $result=4; } } ?> <script type="text/javascript"> window.top.stopUpload(<?php echo $result;?>); </script>
更多：http://zccst.iteye.com/blog/1276920
input file美化看：http://www.oschina.net/code/snippet_273800_20312