CodeIgniter function with @ symbol

Session.php

<?php
// Lines 706-721 of system/libraries/Session.php
function _unserialize($data)
{
	$data = @unserialize(strip_slashes($data));

	if (is_array($data))
	{
		foreach ($data as $key => $val)
		{
			$data[$key] = str_replace('{{slash}}', '\\', $val);
		}

		return $data;
	}

	return str_replace('{{slash}}', '\\', $data);
}