Best way to check for null in PHP

Question

I want to know the best / efficient way to check for null in PHP.

!$var
$var === null
is_null($var)

Don't even know if there are more ways to check it, but I want to use the more efficient one.

Answer 1

I will prefer option two. But I will normally use it this way

null  === $var (yoda condition)

Yoda condition will prevent a possible mistake that you assign a value unintentionally instead of writing a conditional statement.

Frameworks like Wordpress and Symfony use yoda condition as part of their code standard.

Using is_null() function is slower since it is a function. However; the difference is really small.