PHP isset() vs empty() vs is_null() comparison

A PHP isset, empty, and is null helper function comparison with a table for variables and common types.

Quick rundown

isset() returns true when the variable has a value, is not null or a declared and not assigned variable.

empty() empty returns true for an empty string, null, 0 as string and int or false.

is_null() will return true only for a null value or when the variable is declared but not assigned.


Isset is the opposite of is_null, it can be applied to unknown variables to check if they “are set”. is_null can only be used on variables that exist and serves as a method for variables that exist but are not assigned or are null. Empty can be seen as a type of middle ground.

Comparison table

Using PHP version 8.0.0

$var valueisset($var)empty($var)is_null($var)
” (empty)bool(true)bool(true)bool(false)
‘ ‘ (space)bool(true)bool(false)bool(false)