(Keys in PHP arrays are not type sensitive, so pay attention when using them!)

$arr = array(1 => 10, "1" => 11);

Now several questions arise. First of all, how many elements have this array? Two or one. This can be easily verified by checking what count() will return.

echo count($arr);

The correct answer is 1. This simply means, that there’s no difference between string keys and integer keys. What would happen if we had a “normal” array with different keys?

$arr = array(1 => 10, "2" => 11);
echo count($arr);

As expected this returns 2.

Next thing to check is what’s in the array after this initialization line.

$arr = array(1 => 10, "1" => 11);

Is there something in the first element $arr[0], or there’s something in the second element $arr[1]? What is the value of the single value?

As it appears the second element replaces the first one. We’ve seen that the array has only one value, but where’s that value? The only way to check this is to dump both elements:

var_dump($arr);

Here we can see that $arr[1] contains “11″ and it is the only value, and $arr[0] is not set.

Related posts:

1. PHP: What is More Powerful Than list() – Perhaps extract()
2. PHP: What is More Powerful Than list()
3. PHP: The Array Element Doesn’t Exist – Suppress the Warnings

Source: http://www.stoimen.com/blog/2011/10/19/thing-to-know-about-php-arrays/