A table to figure out the difference between PHP is_null, empty, Isset _php instance

Isset to determine if a variable already exists

Empty to determine if the variable is null or 0

Is_null to determine if a variable is null

variables	Empty	Is_null	isset
$a = ""	True	False	True
$a =null	True	True	False
var $a	True	True	False
$a =array ()	True	False	True
$a =false	True	False	True
$a =15	False	False	True
$a =1	False	False	True
$a =0	True	False	True
$a = "0"	True	False	True
$a = "true"	False	False	True
$a = "false"	False	False	True

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