Check variables in PHP / JS for existence03
17

During your daily work with variables in PHP and JavaScript you often come across the query whether a variable is empty. It is worth knowing the native functions and their differences for checking. Annoyingly, there is no simple method to intuitively check whether a variable exists or not. What is meant by this is illustrated in the following matrix. However, small helper functions can be used to retrofit the desired function.

PHP

	=== null	== null	is_null	isset	empty	if/else	ternary	count > 0	== ''	=== ''	@__x
$a	true	true	true	false	true	false	false	false	true	false	false
null	true	true	true	false	true	false	false	false	true	false	false
[]	false	true	false	true	true	false	false	false	false	false	false
0	false	true	false	true	true	false	false	true	true	false	true
1	false	false	false	true	false	true	true	true	false	false	true
-1	false	false	false	true	false	true	true	true	false	false	true
''	false	true	false	true	true	false	false	true	true	true	false
' '	false	false	false	true	false	true	true	true	false	false	false
str	false	false	false	true	false	true	true	true	false	false	true
[0,1]	false	false	false	true	false	true	true	true	false	false	true
[0]	false	false	false	true	false	true	true	true	false	false	true
new stdClass()	false	false	false	true	false	true	true	true	false	false	false

Implementation of __x:

740550c6b3d2b9ae03e4d220eb08e6e3

The helper function __x is called with the error control operator @, which is usually not recommended, in order to check previously undefined variables.

JavaScript

	=== null	== null	typeof input === 'undefined'	if/else	ternary	length > 0	== ''	=== ''	__x
$a	false	true	true	false	false	type error	false	false	false
null	true	true	false	false	false	type error	false	false	false
[]	false	false	false	true	true	false	true	false	false
0	false	false	false	false	false	false	true	false	true
1	false	false	false	true	true	false	false	false	true
-1	false	false	false	true	true	false	false	false	true
''	false	false	false	false	false	false	true	true	false
' '	false	false	false	true	true	true	false	false	false
str	false	false	false	true	true	true	false	false	true
[0,1]	false	false	false	true	true	true	false	false	true
[0]	false	false	false	true	true	true	false	false	true
new Object()	false	false	false	true	true	false	false	false	false

Implementation of __x:

740550c6b3d2b9ae03e4d220eb08e6e3

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VielhuberDavid

Check variables in PHP / JS for existence0317

PHP

JavaScript

Check variables in PHP / JS for existence03
17