Array Specials

<?php
echo "<pre>";
$array = array ('3' => 'a', 3 => 'b', 3.5=>"c", "3.5"=>"d", -3=>"e", -3.5=>"f", "-3"=>"g", "-3.5"=>"h");
print_r($array);
?>

Array
(
    [3] => c
    [3.5] => d
    [-3] => g
    [-3.5] => h
)

$array = array (true => 'a', 1 => 'b', "1" => 'c');
var_dump ($array); //c

$array = array (true => 'a', 1 => 'b');
var_dump ($aray); //wrong variable, NULL


$array = array ("" => 'a', null => 'b');
var_dump ($array); //b, NULL converted to emptry string