uploadify : restrict image dimension - uploadify

Question

I am using Uploadify to upload image in php(codeigniter). Tested with the sample php file that come with the uploadify package. It works. However, I can't get onUploadError triggered. The sample php code has:
if (in_array($file_ext,$fileTypes)) {
$newFileName = mt_rand() . time() . '.' . $file_ext;
$targetFile = rtrim($targetPath,'/') . '/' . $newFileName;
move_uploaded_file($tempFile,$targetFile);
echo $newFileName;
} else {
echo 'Invalid file type.';
}
js is very simple as following:
$('#file_upload').uploadify({
'fileTypeDesc' : 'Image Files',
'fileTypeExts' : '*.gif; *.jpg; *.jpeg; *.png',
'swf' : '/static/uploadify/uploadify.swf',
'uploader' : '/static/uploadify/uploadify.php',
'onUploadError' : function(file, errorCode, errorMsg, errorString) {
console.log('The file ' + file.name + ' errorCode ' + errorCode + ' errorMsg ' + errorMsg + ' errorString ' + errorString);
},
'onUploadSuccess' : function(file, data, response) {
console.log(data);
}
});
when the Invalid file type. is echoed to the frontend. the onUploadSuccess is triggered instead of onUploadError. It seems odd to me that there is no indicator to stell uploadify there is an error from php.
the only way that triggers onUploadError is to set a non 200 http header before echoing. however, onUploadError function arguments errorCode, errorMsg, errorString are the http code and the echo content(error message) is lost.
UPDATES
I modified the question title so it speaks the real problem I was trying to solve. And I have since found the solution.

Answer 1

I finally got sometime to tackle this problem and here are my steps to solve it.
first, the problem of onUploadError is not fired is because the file has been uploaded successfully
second, uploadify queue limit and upload limit are updated accordingly upon successful upload regardless of detection of wrong image dimension from the backend.
So the solution is that my backend checks image dimension and responds with a json data with error message which shown to user. also reset uploadify, really it is swfupload, variable successful_uploads. that makes sure the queuelimit or upload limit not messed up. sample code:
'onUploadSuccess' : function(file, data, response) {
var obj = eval('(' + data + ')');
if ( obj.success ) { alert('uploaded') }
else {
var stats = this.getStats();
this.setStats({successful_uploads: stats.successful_uploads - 1});
}
}
see swfupload setStats method http://demo.swfupload.org/Documentation/#setStats