initialize variable?????

i have a script that gets users information witch someone has helped me with but they have put a comment “// initialize variable” and can i ask what i suppposed to put there? thanks

heres the bit of the code:

[code=php]
$query = “SELECT * FROM `users`”; // get all user information
$result = mysql_query($query);
$userarray; // initialize variable

while($row = mysql_fetch_array($result))
{
$userarray[$row[‘x’] . ‘,’ . $row[‘y’]] = true;
// load all the user info we need into an array
}[/code]

Also in #PHP _↴