While you can call functions in front or after current code you cannot do so with classes. As this is documented nowhere this is an error with both ZE1 and ZE2.

Following .phpt file:
====================================
--TEST--
Method call infront of class definition
--FILE--
<?php

test::show_static();

$t = new test;
$t->show_method();

class test {
	function show_static() {
		echo "static\n";
	}
	function show_method() {
		echo "method\n";
	}
}
?>
--EXPECT--
static
method 
=EOF================================

Produces following .out
====================================
<font color=ff0000>
Fatal error: Class 'test' not found in /usr/src/php4-HEAD/tests/classes/classes001.php on line 3
</font>/usr/src/php4-HEAD/tests/classes/classes001.php(3) : Fatal error - Class 'test' not found
=EOF================================