Question

Possible Duplicate:
Strange behavior with isset() returning true for an Array Key that does NOT exist

$arr = array(
         'application' => array (
            'environment' => 'development',
            'mode_debug' => 1,
            'key' => '123456abcdefg',
            'debug_soft' =>
            'firephp',
            'aaa' => array (
                'bbb' => '111',
                'ccc' => '222',
                'ddd' => array (
                    'eee' => '12345',
                ),
            ),
        ),
        'database' => array (
            'host' => 'localhost',
            'database' => '',
            'username' => '',
            'password' => '',
            'charset' => 'utf8',
            'prefix' => '',
        ),
    );


if(isset($arr["application"]["aaa"]["ddd"]["eee"]['out']) && !empty($arr["application"]["aaa"]["ddd"]["eee"]['out'])){
    echo "a";
    echo '<br />';
    var_dump($arr["application"]["aaa"]["ddd"]["eee"]['out']);
}else{
    echo "b";
}

returns:

a
string(1) "1" 

but there is no ‘out’ index in the ‘$arr’ array, so why it returns ‘string(1) “1”‘?

The manual doesn’t help, because it only samples one dimentional array:

$a = array ('test' => 1, 'hello' => NULL);

var_dump( isset ($a['test']) );            // TRUE
var_dump( isset ($a['foo']) );             // FALSE
var_dump( isset ($a['hello']) );           // FALSE

Answer 1

Consider this:

$str = 'test';
var_dump(isset($str['xxx'])); // true

It returns true, because:

• PHP supports $str[$n] syntax (to address individual characters of the string)

• when calculating index, it’s cast to integer type

• when cast to integer, "xxx" is 0; you’re accessing $str[0] – the first character of that $str string, and it (t) is a truthy value.

Note that this (quite weird) behavior of isset was fixed in PHP 5.4:

5.4.0: Checking non-numeric offsets of strings now returns FALSE.