gettype and unknown type in php

Question

I\'ve just started to practice with PHP built-in gettype() and its return value. This function is capable to return testing result such as boolean,

Answer 1

According to the PHP source code it's the "default" case in the switch statement for that function. My guess is that is is there way of handling an internal error.

Answer 2

Here is one unknown type for you:

$f = fopen('somefile.txt','r');
echo gettype($f); // resource
fclose($f); 
echo gettype($f); // unknown

Basically, whenever a resource pointer is closed, the variable holding the handle will point to an unknown resource. Another example would be with GD'S imagecreate/imagedestroy.

Note: as of PHP 7.2, this no longer holds true. gettype will return resource (closed) then.