I'm working with images already uploaded to my server, not remote.

I'm reading that getimagesize() is very slow, but I'm not sure if that only applies to remote images:

[php.net...]

Any suggestions on the fastest option to get the image dimensions when the image is stored locally?

I currently use:

if (is_readable($path_to . $img)) {
 list($width, $height) = @getimagesize($path_to . $img);
 // do stuff
}

The majority of the time, the image would be readable. If it's not then it means that there was a glitch in the server somewhere during the user's upload. Should I even test that it's readable first? Or am I wasting resources trying to prevent that 0.00001%?

Considered alternative:

if (list($width, $height) = @getimagesize($path_to . $img)) {
 // do stuff
}