php之间的区别！$ a和$ a === false [复制]

Question

Possible Duplicate:
Is !$page == false or $page in php?

What is the difference between these two types of checks? And which would be the correct way of type checking called functions or methods that fail and return false?

if (!is_dir($path)) {...}

or

if (is_dir($path) === false) {...}

Answer 1

!$a will be true if $a is set to 0, or if $a is unset. The triple equal sign strictly checks for false, not just for null-ish values.