PHP Image Resize and Crop

<?php
############ Configuration ##############
$thumb_square_size      = 200; //Thumbnails will be cropped to 200x200 pixels
$max_image_size         = 500; //Maximum image size (height and width)
$thumb_prefix           = "thumb_"; //Normal thumb Prefix
$destination_folder     = 'uploads/'; //upload directory ends with / (slash)
$jpeg_quality           = 90; //jpeg quality
##########################################

//continue only if $_POST is set and it is a Ajax request
if(isset($_POST) && isset($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest'){

    // check $_FILES['ImageFile'] not empty
    if(!isset($_FILES['image_file']) || !is_uploaded_file($_FILES['image_file']['tmp_name'])){
            die('Image file is Missing!'); // output error when above checks fail.
    }

    //uploaded file info we need to proceed
    $image_name = $_FILES['image_file']['name']; //file name
    $image_size = $_FILES['image_file']['size']; //file size
    $image_temp = $_FILES['image_file']['tmp_name']; //file temp

    $image_size_info    = getimagesize($image_temp); //get image size

    if($image_size_info){
        $image_width        = $image_size_info[0]; //image width
        $image_height       = $image_size_info[1]; //image height
        $image_type         = $image_size_info['mime']; //image type
    }else{
        die("Make sure image file is valid!");
    }

    //switch statement below checks allowed image type
    //as well as creates new image from given file
    switch($image_type){
        case 'image/png':
            $image_res =  imagecreatefrompng($image_temp); break;
        case 'image/gif':
            $image_res =  imagecreatefromgif($image_temp); break;
        case 'image/jpeg': case 'image/pjpeg':
            $image_res = imagecreatefromjpeg($image_temp); break;
        default:
            $image_res = false;
    }

    if($image_res){
        //Get file extension and name to construct new file name
        $image_info = pathinfo($image_name);
        $image_extension = strtolower($image_info["extension"]); //image extension
        $image_name_only = strtolower($image_info["filename"]);//file name only, no extension

        //create a random name for new image (Eg: fileName_293749.jpg) ;
        $new_file_name = $image_name_only. '_' .  rand(0, 9999999999) . '.' . $image_extension;

        //folder path to save resized images and thumbnails
        $thumb_save_folder  = $destination_folder . $thumb_prefix . $new_file_name;
        $image_save_folder  = $destination_folder . $new_file_name;

        //call normal_resize_image() function to proportionally resize image
        if(normal_resize_image($image_res, $image_save_folder, $image_type, $max_image_size, $image_width, $image_height, $jpeg_quality))
        {
            //call crop_image_square() function to create square thumbnails
            if(!crop_image_square($image_res, $thumb_save_folder, $image_type, $thumb_square_size, $image_width, $image_height, $jpeg_quality))
            {
                die('Error Creating thumbnail');
            }

            /* We have succesfully resized and created thumbnail image
            We can now output image to user's browser or store information in the database*/
            echo '<div align="center">';
            echo '<img src="uploads/'.$thumb_prefix . $new_file_name.'" alt="Thumbnail">';
            echo '<br />';
            echo '<img src="uploads/'. $new_file_name.'" alt="Resized Image">';
            echo '</div>';
        }

        imagedestroy($image_res); //freeup memory
    }
}

#####  This function will proportionally resize image #####
function normal_resize_image($source, $destination, $image_type, $max_size, $image_width, $image_height, $quality){

    if($image_width <= 0 || $image_height <= 0){return false;} //return false if nothing to resize

    //do not resize if image is smaller than max size
    if($image_width <= $max_size && $image_height <= $max_size){
        if(save_image($source, $destination, $image_type, $quality)){
            return true;
        }
    }

    //Construct a proportional size of new image
    $image_scale    = min($max_size/$image_width, $max_size/$image_height);
    $new_width      = ceil($image_scale * $image_width);
    $new_height     = ceil($image_scale * $image_height);

    $new_canvas     = imagecreatetruecolor( $new_width, $new_height ); //Create a new true color image

    //Copy and resize part of an image with resampling
    if(imagecopyresampled($new_canvas, $source, 0, 0, 0, 0, $new_width, $new_height, $image_width, $image_height)){
        save_image($new_canvas, $destination, $image_type, $quality); //save resized image
    }

    return true;
}

##### This function corps image to create exact square, no matter what its original size! ######
function crop_image_square($source, $destination, $image_type, $square_size, $image_width, $image_height, $quality){
    if($image_width <= 0 || $image_height <= 0){return false;} //return false if nothing to resize

    if( $image_width > $image_height )
    {
        $y_offset = 0;
        $x_offset = ($image_width - $image_height) / 2;
        $s_size     = $image_width - ($x_offset * 2);
    }else{
        $x_offset = 0;
        $y_offset = ($image_height - $image_width) / 2;
        $s_size = $image_height - ($y_offset * 2);
    }
    $new_canvas = imagecreatetruecolor( $square_size, $square_size); //Create a new true color image

    //Copy and resize part of an image with resampling
    if(imagecopyresampled($new_canvas, $source, 0, 0, $x_offset, $y_offset, $square_size, $square_size, $s_size, $s_size)){
        save_image($new_canvas, $destination, $image_type, $quality);
    }

    return true;
}

##### Saves image resource to file #####
function save_image($source, $destination, $image_type, $quality){
    switch(strtolower($image_type)){//determine mime type
        case 'image/png':
            imagepng($source, $destination); return true; //save png file
            break;
        case 'image/gif':
            imagegif($source, $destination); return true; //save gif file
            break;
        case 'image/jpeg': case 'image/pjpeg':
            imagejpeg($source, $destination, $quality); return true; //save jpeg file
            break;
        default: return false;
    }
}