Using isset() empty() and is_null()

Validating the input is very important, but you want te write lean code. So if you are in doubt
about using !empty only, or !empty && isset here’s the difference:

Value of variable ($var)isset($var)empty($var)is_null($var)
“” (an empty string)bool(true)bool(true)bool(false)
” ” (space)bool(true)bool(false)bool(false)
array() (an empty array)bool(true)bool(true)bool(false)
“0” (0 as a string)bool(true)bool(true)bool(false)
0 (0 as an integer)bool(true)bool(true)bool(false)
0.0 (0 as a float)bool(true)bool(true)bool(false)
var $var; (a variable declared, but without a value)bool(false)bool(true)bool(true)
NULL byte (“\ 0”)bool(true)bool(false)bool(false)