js基础代码：
jQuery.extend({
???createUploadIframe: function(id, uri)
???{
???????//create frame
???????var frameId = ‘jUploadFrame‘ + id;
???????var iframeHtml = ‘<iframe id="‘ + frameId + ‘" name="‘ + frameId + ‘" style="position:absolute; top:-9999px; left:-9999px"‘;
???????if(window.ActiveXObject)
???????{
???????????if(typeof uri== ‘boolean‘){
???????????????iframeHtml += ‘ src="‘ + ‘javascript:false‘ + ‘"‘;
???????????}
???????????else if(typeof uri== ‘string‘){
???????????????iframeHtml += ‘ src="‘ + uri + ‘"‘;
???????????}
???????}
???????iframeHtml += ‘ />‘;
???????jQuery(iframeHtml).appendTo(document.body);
???????return jQuery(‘#‘ + frameId).get(0);
???},
???createUploadForm: function(id, fileElementId)
???{
???????//create form
???????var formId = ‘jUploadForm‘ + id;
???????var fileId = ‘jUploadFile‘ + id;
???????var form = jQuery(‘<form ?action="" method="POST" name="‘ + formId + ‘" id="‘ + formId + ‘" enctype="multipart/form-data"></form>‘);
???????var oldElement = jQuery(‘#‘ + fileElementId);
???????var newElement = jQuery(oldElement).clone();
???????jQuery(oldElement).attr(‘id‘, fileId);
???????jQuery(oldElement).before(newElement);
???????jQuery(oldElement).appendTo(form);
???????//添加参数支持
???????/*if(data){
???????????$.each(data,function(key,value){
???????????????$("<input type=‘hidden‘ name=‘"+key+"‘ value=‘"+value+"‘/>").appendTo(form);
???????????})
???????}*/
???????//set attributes
???????jQuery(form).css(‘position‘, ‘absolute‘);
???????jQuery(form).css(‘top‘, ‘-1200px‘);
???????jQuery(form).css(‘left‘, ‘-1200px‘);
???????jQuery(form).appendTo(‘body‘);
???????return form;
???},
???ajaxFileUpload: function(s) {
???????// TODO introduce global settings, allowing the client to modify them for all requests, not only timeout
???????s = jQuery.extend({}, jQuery.ajaxSettings, s);
???????var id = new Date().getTime()
???????var form = jQuery.createUploadForm(id, s.fileElementId,s.data);
???????var io = jQuery.createUploadIframe(id, s.secureuri);
???????var frameId = ‘jUploadFrame‘ + id;
???????var formId = ‘jUploadForm‘ + id;
???????// Watch for a new set of requests
???????if ( s.global && ! jQuery.active++ )
???????{
???????????jQuery.event.trigger( "ajaxStart" );
???????}
???????var requestDone = false;
???????// Create the request object
???????var xml = {}
???????if ( s.global )
???????????jQuery.event.trigger("ajaxSend", [xml, s]);
???????// Wait for a response to come back
???????var uploadCallback = function(isTimeout)
???????{
???????????var io = document.getElementById(frameId);
???????????try
???????????{
???????????????if(io.contentWindow)
???????????????{
???????????????????xml.responseText = io.contentWindow.document.body?io.contentWindow.document.body.innerHTML:null;
???????????????????xml.responseXML = io.contentWindow.document.XMLDocument?io.contentWindow.document.XMLDocument:io.contentWindow.document;
???????????????}else if(io.contentDocument)
???????????????{
???????????????????xml.responseText = io.contentDocument.document.body?io.contentDocument.document.body.innerHTML:null;
???????????????????xml.responseXML = io.contentDocument.document.XMLDocument?io.contentDocument.document.XMLDocument:io.contentDocument.document;
???????????????}
???????????}catch(e)
???????????{
???????????????jQuery.handleError(s, xml, null, e);
???????????}
???????????if ( xml || isTimeout == "timeout")
???????????{
???????????????requestDone = true;
???????????????var status;
???????????????try {
???????????????????status = isTimeout != "timeout" ? "success" : "error";
???????????????????// Make sure that the request was successful or notmodified
???????????????????if ( status != "error" )
???????????????????{
???????????????????????// process the data (runs the xml through httpData regardless of callback)
???????????????????????var data = jQuery.uploadHttpData( xml, s.dataType );
???????????????????????// If a local callback was specified, fire it and pass it the data
???????????????????????if ( s.success )
???????????????????????????s.success( data, status );
???????????????????????// Fire the global callback
???????????????????????if( s.global )
???????????????????????????jQuery.event.trigger( "ajaxSuccess", [xml, s] );
???????????????????} else
???????????????????????jQuery.handleError(s, xml, status);
???????????????} catch(e)
???????????????{
???????????????????status = "error";
???????????????????jQuery.handleError(s, xml, status, e);
???????????????}
???????????????// The request was completed
???????????????if( s.global )
???????????????????jQuery.event.trigger( "ajaxComplete", [xml, s] );
???????????????// Handle the global AJAX counter
???????????????if ( s.global && ! --jQuery.active )
???????????????????jQuery.event.trigger( "ajaxStop" );
???????????????// Process result
???????????????if ( s.complete )
???????????????????s.complete(xml, status);
???????????????jQuery(io).unbind()
???????????????setTimeout(function()
???????????????{ ?try
???????????????{
???????????????????jQuery(io).remove();
???????????????????jQuery(form).remove();
???????????????} catch(e)
???????????????{
???????????????????jQuery.handleError(s, xml, null, e);
???????????????}
???????????????}, 100)
???????????????xml = null
???????????}
???????}
???????// Timeout checker
???????if ( s.timeout > 0 )
???????{
???????????setTimeout(function(){
???????????????// Check to see if the request is still happening
???????????????if( !requestDone ) uploadCallback( "timeout" );
???????????}, s.timeout);
???????}
???????try
???????{
???????????var form = jQuery(‘#‘ + formId);
???????????jQuery(form).attr(‘action‘, s.url);
???????????jQuery(form).attr(‘method‘, ‘POST‘);
???????????jQuery(form).attr(‘target‘, frameId);
???????????if(form.encoding)
???????????{
???????????????jQuery(form).attr(‘encoding‘, ‘multipart/form-data‘);
???????????}
???????????else
???????????{
???????????????jQuery(form).attr(‘enctype‘, ‘multipart/form-data‘);
???????????}
???????????jQuery(form).submit();
???????} catch(e)
???????{
???????????jQuery.handleError(s, xml, null, e);
???????}
???????jQuery(‘#‘ + frameId).load(uploadCallback ?);
???????return {abort: function () {}};
???},
???uploadHttpData: function( r, type ) {
???????var data = !type;
???????data = type == "xml" || data ? r.responseXML : r.responseText;
???????// If the type is "script", eval it in global context
???????if ( type == "script" )
???????????jQuery.globalEval( data );
???????// Get the JavaScript object, if JSON is used.
???????if ( type == "json" )
???????????eval( "data = " + data );
???????// evaluate scripts within html
???????if ( type == "html" )
???????????jQuery("<div>").html(data).evalScripts();
???????return data;
???}
})
html部分：
$.ajaxFileUpload({
???????url:"{:U(‘Web/Project/ajax_upload‘)}", //你处理上传文件的服务端
???????secureuri:false,
???????fileElementId:‘back_img‘,//imput file 的 name
???????dataType: ‘json‘,
???????success: function (data)
???????{
???????????if(data.code == 200) {
??????????????//success todo
???????????}
???????}
});
php：public function ajax_upload() {
???$images = upload_img(‘ajax‘);
???echo json_code([‘code‘ => 200]);
}参考来源：
http://www.jb51.net/article/51180.htm
ajax+php上传文件
原文地址：http://www.cnblogs.com/yuanlai/p/7600656.html