テンプレート変数のimageの幅と高さを取得したい

//imgWrapper
//example
//[!imgWrapper? &src=`[*lastDateImg*]` &alt=`[*lastDateImgAlt*]`!]

<?php
if (! isset($src))
    return;
list($w,$h)=getimagesize($src);
$width = isset($width)? $width : $w;
$height = isset($height)? $height : $h;
$alt = isset($alt)? $alt : "";
$tag = isset($class)?  '<img src="' . $src . '" width="' . $width . '" height="' . $height . '" alt="' . $alt . '" class="' . $class . '" />' :  '<img src="' . $src . '" width="' . $width . '" height="' . $height . '" alt="' . $alt . '" />';
return "$tag";
?>