Check if value isset and null

Question

I need to check if value is defined as anything, including null. isset treats null values as undefined and returns false. Take the following as an example:

$foo = null;  if(isset($foo)) // returns false if(isset($bar)) // returns false if(isset($foo) || is_null($foo)) // returns true if(isset($bar) || is_null($bar)) // returns true, raises a notice 

Note that $bar is undefined.

I need to find a condition that satisfies the following:

if(something($bar)) // returns false; if(something($foo)) // returns true; 

Any ideas?

Answer 1

IIRC, you can use get_defined_vars() for this:

$foo = NULL; $vars = get_defined_vars(); if (array_key_exists('bar', $vars)) {}; // Should evaluate to FALSE if (array_key_exists('foo', $vars)) {}; // Should evaluate to TRUE 

Answer 2

If you are dealing with object properties which might have a value of NULL you can use: property_exists() instead of isset()

<?php  class myClass {     public $mine;     private $xpto;     static protected $test;      function test() {         var_dump(property_exists($this, 'xpto')); //true     } }  var_dump(property_exists('myClass', 'mine'));   //true var_dump(property_exists(new myClass, 'mine')); //true var_dump(property_exists('myClass', 'xpto'));   //true, as of PHP 5.3.0 var_dump(property_exists('myClass', 'bar'));    //false var_dump(property_exists('myClass', 'test'));   //true, as of PHP 5.3.0 myClass::test();  ?> 

As opposed with isset(), property_exists() returns TRUE even if the property has the value NULL.