What does "?:" mean in PHP? [duplicate]

Question

While browsing the code of an open source PHP library I spotted this line:

$path = $path ?: $this->guessPackagePath();

This is not the ternary operator like it usually apprears. Would anyone explain what is going on in it?

Answer 1

It's a shortcut for

$path = $path ? $path : $this->guessPackagePath();

which comes from PHP 5.3