a Set class that maintains an array of unique items

<?php
class Set
{
	protected $_storage_array;
 
	function __constructor()
	{
		$this->_storage_array = array();
	}
 
	function add($value)
	{
		$this->_storage_array[$value] = $value;
	}
 
	function hasValue($value)
	{
		return in_array($value, array_keys($this->_storage_array));
	}
 
	function toArray()
	{
		return array_keys($this->_storage_array);
	}
}
 
$data = new Set;
$data->add("Sarah");
$data->add("Jamie");
$data->add("Phil");
$data->add("Jamie");
 
print("Has Value Jamie? " . ($data->hasValue("Jamie") ? 'true' : 'false')) . PHP_EOL;
print_r($data->toArray());
 
/*
Returns the following:
 
Has Value Jamie? true
Array
(
    [0] => Sarah
    [1] => Jamie
    [2] => Phil
)
*/
?>