Ajax上传图片失败

I am trying to upload image on server using ajax post.

I am facing problem with big size images. For example i can upload 1MB image without problem, but when i try to upload 5MB image file $_FILES['errors'] return Please select file message.

The ajax call i currently use.

    var request = $.ajax({
        url: '/uploadguides',
        dataType: 'json',
        cache: false,
        contentType: false,
        processData: false,
        data: formData,
        type: 'post',
        async: false
    });

In php.ini i have set post_max_size = 3M, upload_max_filesize = 64M.

I thought it was post_max_size limit problem i have increased it to 20M but same result

First - I found this by Googling getting images:

https://github.com/blueimp/JavaScript-Load-Image

Second, why use AJAX? Doesn't the built-in Javascript Image set up automatically load in an image when you change the source? Like so:

var img = new Image();
img.src = "Path to image";

If you use the above - all you do is to check the width of the image in order to know it has been loaded. Just make a little function to check if the file has been loaded like so:

function checkImage()
{
     if( img.width < 1 ){
        setTimeout( "checkImage()", 100 );
        return;
        }

     tellMeItIsLoaded();
}

Or take a look at this article

Load Image from javascript