comparison_list.md

PHP: Comparison list

This mem by @Fell PHP: isset、is_null、if($var)、empty 比較一覧表

Comparison list

	Value or element	Type		isset	is_null	empty	if($var)		!empty
1	$var	undefined(null)		false	error(true)	true	error(false)		false
2	$var = NULL	null		false	true	true	false		false
3	$var = "";	string		true	false	true	false		false
4(*)	$var = 0;	int		true	false	true	false		false
5(*)	$var = '0'	string		true	false	true	false		false
6	$var = 1	int		true	false	false	true		true
7	$var = '1'	string		true	false	false	true		true
8	$var = array()	array		true	false	true	false		false
9	$var = array(1)	array		true	false	false	true		true

Comment 1

isset and empty

empty($var) is !isset($var) || $var == false

!empty($var) is isset($var) && $var == true

• !isset is safer than is_null
• !empty is a double check of null check and if($var).
• Be careful of $var = 0 and $var = "0" in (*).

Summary

• isset is a null check including undefined.
• empty is a check when there is no value, including undefined.
• if($var) is a check when there is a value without undefined check.
• !empty is a check when there is a value with undefined check.
• The judgment part in (*) is quite delicate, and it is judged that there is no numerical 0 or "0" in the character string.

Variable in class

Getter

	value	type		isset	is_null	empty	if($var)		!empty
1	$var	未定義(null)		false	true	true	false		false
2	$var = NULL	null		false	true	true	false		false
3	$var = "";	string		false	false	true	false		false
4(*)	$var = 0;	int		false	false	true	false		false
5(*)	$var = "0";	int		false	false	true	false		false
6	$var = 1;	int		false	false	true	true		false
7	$var = "1";	int		false	false	true	true		false
8	$var = array()	array		false	false	true	false		false
9(*)	$var = array(1)	array		false	false	true	true		false

Comment 2

• With getters, it's different !is_null and if($var) are likely to be same.
• isset doesn't work at all. Use !is_null.
• Since empty is also an array with contents and the behavior is strange, if($var) seems to be good.
• Again, be careful of $var = 0, $var = "0" and $var = array(1) in (*).

Reference

PHP