There is no clear format for the header-array required. But the constructor will fail anyway because of a curious call to explode().

list($name, $value) = explode(": ", $value, 1);

From the PHP manual ([http://www.php.net/manual/en/function.explode.php]): ??If limit is set and positive, the returned array will contain a maximum of limit elements with the last element containing the rest of string.??

With the limit-parameter set to one explode() will always return an array having exactly one element. The list-keyword on the left side of the assignment expects two elements. Thus, no matter what $value contains this will issue PHP to complaining with "Undefined offset: 1".