In case anyone is wondering what values these constants have
<?php
$imagetypes = array('IMG_AVIF', 'IMG_BMP', 'IMG_GIF', 'IMG_JPG', 'IMG_PNG', 'IMG_WBMP', 'IMG_XPM', 'IMG_WEBP');
foreach ($imagetypes as $imagetype) {
echo constant($imagetype) . "\t" . $imagetype . "\r\n";
}
/* would output
256 IMG_AVIF
64 IMG_BMP
1 IMG_GIF
2 IMG_JPG
4 IMG_PNG
8 IMG_WBMP
16 IMG_XPM
32 IMG_WEBP
*/
?>