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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