Is saying “if ( $a != null && $a == 5)” the same as “if ($a == 5)”

Question

First off, sorry if this is answered somewhere else. I did a brief search, but wasn't sure how to ask in search terms.

I'm looking at some code and came across lot's of statements like this:

if ( ($a != empty_or_null_or_notDefined && $a == 5 )

Is this the same as just saying:

if ( $a == 5 )

?

(language is PHP.)