Assigning array() before using a variable like array

Question

I tried to find a proper and explanatory title but I couldn't and I will try to explain what I am asking here:

Normally if you don't assign an empty array to a variable, you can start assign values to indexes like this:

$hello["world"] = "Hello World";
...
echo $hello["world"];

but I always encounter such definition:

$hello = array() //assigning an empty array first
$hello["hello"] = "World";
...
echo $hello["hello"];

Why is it used a lot. Is there a performance gain or something with the second one?

Thanks.

Answer 1

Two reasons:

• Better readability (you know the array is initialized at this point)
• Security - when running on a system with register_globals enabled a user could add e.g. hello[moo]=something to the query string and the array would already be initialized with this. $hello = array(); overwrites this value though since a new array is created.