PHP isset() vs empty() vs is_null() vs if($var) vs ??

See blog article for explanation.

PHP version is 7.4.33

Value of variable ($var)	isset($var)	empty($var)	is_null($var)	if($var)	$var ?? '-' Null Coalesce Operator (since PHP 7.0)
'' (an empty string)	bool(true)	bool(true)	bool(false)	false	string(0) ""
" " (space)	bool(true)	bool(false)	bool(false)	true	string(1) " "
" " (two spaces)	bool(true)	bool(false)	bool(false)	true	string(2) " "
false	bool(true)	bool(true)	bool(false)	false	bool(false)
FALSE	bool(true)	bool(true)	bool(false)	false	bool(false)
true	bool(true)	bool(false)	bool(false)	true	bool(true)
TRUE	bool(true)	bool(false)	bool(false)	true	bool(true)
array() (an empty array)	bool(true)	bool(true)	bool(false)	false	array(0) { }
new stdClass() (an empty object)	bool(true)	bool(false)	bool(false)	true	object(stdClass)#140 (0) { }
NULL	bool(false)	bool(true)	bool(true)	false	string(1) "-"
"0" (0 as a string)	bool(true)	bool(true)	bool(false)	false	string(1) "0"
0 (0 as an integer)	bool(true)	bool(true)	bool(false)	false	int(0)
0.0 (0 as a float)	bool(true)	bool(true)	bool(false)	false	float(0)
var $var; (a variable declared, but without a value)	bool(false)	bool(true)	bool(true)	false	string(1) "-"
NULL byte ("\0")	bool(true)	bool(false)	bool(false)	true	string(1) ""

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