Imagejpeg function not changing file extension

Question

I am creating a image convert function. File extension not changing eg oldfile.png out newfile.png . But it should change the extension after file convert eg newfile.jpg right?

function convertimg($target, $new, $ext, $converto) {
    if ($ext['mime'] == 'image/jpeg') {
        $img = imagecreatefromjpeg($target);
    } elseif ($ext['mime'] == 'image/png') {
        $img = imagecreatefrompng($target);
    } elseif ($ext['mime'] == 'image/gif') {
        $img = imagecreatefromgif($target);
    }
    $ictc = imagecreatetruecolor($ext[0], $ext[1]);
    imagecopyresampled($ictc, $img, 0, 0, 0, 0, $ext[0], $ext[1], $ext[0], $ext[1]);
    ob_start();
    header("Content-type: " . $converto);
    if ($converto == 'image/jpeg') {
        imagejpeg($ictc, $new, 84);
    } elseif ($converto == 'image/png') {
        imagepng($ictc, $new, 84);
    } elseif ($converto == 'image/gif') {
        imagegif($ictc, $new, 84);
    }
    ob_get_clean();
    imagedestroy($ictc);
}

Answer 1

No it should not, since you supply the new file name, it could be anything.

So if you are converting, you must also supply a new extendsion. The only thing imagegpeg does is saving raw image to a jpeg format.