使用PHP验证进行AJAX文件上载

Question

I have a form that has two text fields and a file upload field.

The validation is handled completely from PHP and I'm using a little bit of Ajax to retrieve the error messages the PHP script produces via an array (err[]).

My problem is, I can't seem to get the file upload validation to work correctly. (when uploading a file, it will always say "Wrong file format only .png , .gif, .jpg, .jpeg are accepted")

The Ajax is below:

function checkform() {
        $.post('upload.php', $("form#uploadForm").serialize(), function (data) {

                $("div#error").html(data).slideDown("fast");

                var destination = $('div#uploadContainer').offset().top - 15;
                $("html:not(:animated),body:not(:animated)").animate({
                    scrollTop: destination
                }, 200);

            });
    return false;
}

The following validation seems to ALWAYS be triggered:

$extension = strrchr($_FILES['uploadFile']['name'], '.');
    if (!in_array($extension, $extensions)) {
        $err[]='Wrong file format only .png , .gif, .jpg, .jpeg are accepted';
    }
...
...

Answer 1

if (isset($_FILES['uploadFile']) && $_FILES['uploadFile']['size'] != 0)
{
    // Upload file
}