Is static array property not possible in php?

Below is my code in php,and I am getting error:

Parse error: syntax error, unexpected '[' in /LR_StaticSettings.php on line 4

<?php
class StaticSettings{
    function setkey ($key, $value) {
        self::arrErr[$key] = $value; // error in this line
    }
}
?>

I want to use statically not $this->arrErr[$key] so that I can get and set static properties without creating instance/object.

Why is this error? Can't we create static array?

If there is another way, please tell me. Thanks