Fatal error: Call to undefined function getiamgesize() in D:\www\shopImooc\test\resizeImage1.php on line 3

<?php
$filename="ad.jpg";
list($src_w,$src_h,$imagetype)=getiamgesize($filename);
$mime=image_type_to_mime_type($imagetype);
echo $mime;

运行报错，怎么办呢