php - Are isset() and !== null equivalent? -

since isset appears function (http://php.net/manual/en/function.isset.php), there might overhead calling it. wonder if using !== null instead of isset produce faster code while, importantly, keeping code's behavior same?

from php manual:

isset — determine if variable set , not null

isset returns true if var exists , has value other null, false otherwise.

http://php.net/manual/en/function.isset.php

the function call overhead small don't need worry it. read post: why php function calls *so* expensive?

note isset not function (it has special opcode it), it's faster.