PHP : Dynamic Image Resize

gistfile1

<?php

function getExtension($str) {
         $i = strrpos($str,".");
         if (!$i) { return ""; }
         $l = strlen($str) - $i;
         $ext = substr($str,$i+1,$l);
         return $ext;
	}


function resizeImage($imgSrc,$thumbnail_width,$thumbnail_height, $extension) { //$imgSrc is a FILE - Returns an image resource.
    //getting the image dimensions
    list($width_orig, $height_orig) = getimagesize($imgSrc);

    if($extension == "jpg" || $extension =="jpeg"){
    	$myImage = imagecreatefromjpeg($imgSrc);
    } elseif ($extension == "png") {
    	$myImage = imagecreatefrompng($imgSrc);
    } else{
    	$myImage = imagecreatefromgif($imgSrc);
    }

    $ratio_orig = $width_orig/$height_orig;

    if ($thumbnail_width/$thumbnail_height > $ratio_orig) {
       $new_height = $thumbnail_width/$ratio_orig;
       $new_width = $thumbnail_width;
    } else {
       $new_width = $thumbnail_height*$ratio_orig;
       $new_height = $thumbnail_height;
    }

    $x_mid = $new_width/2;  //horizontal middle
    $y_mid = $new_height/2; //vertical middle

    $process = imagecreatetruecolor(round($new_width), round($new_height));

    //if($extension == "jpg" || $extension =="jpeg") {
    imagecopyresampled($process, $myImage, 0, 0, 0, 0, $new_width, $new_height, $width_orig, $height_orig);
    $thumb = imagecreatetruecolor($thumbnail_width, $new_height);
    imagecopyresampled($thumb, $process, 0, 0, ($x_mid-($thumbnail_width/2)), 0, $thumbnail_width, $new_height, $thumbnail_width, $new_height);

    imagedestroy($process);
    imagedestroy($myImage);
    return $thumb;
}




$image = $_Post['image']['name'];
				
$extension = getExtension($image);
$extension = strtolower($extension);
//if it is not a known extension, we will suppose it is an error and will not upload the file,
//otherwise we will do more tests
if (($extension == "jpg") || ($extension == "jpeg") || ($extension == "png") || ($extension = "gif"))
    {
    	$temp= resizeImage($_Post['image']['tmp_name'], 585,330, $extension);
    	$path_parts = pathinfo($image);
    	$fileImage = $path_parts['filename'];
        $imgfile= 'images/'.$fileImage.'.jpg';
        imagejpeg ( $temp, $imgfile );
    }
}