bar_Test.php

<?php
namespace bar;
class Test {}

foo_AnotherTest.php

<?php
namespace foo;
use bar\Test;
class AnotherTest {}

foo_Test.php

<?php
namespace foo;
class Test {}

main.php

<?php
require './foo_Test.php';    // これを"foo_AnotherTest.php"より「先に」読み込むとエラーになる
require './bar_Test.php';
require './foo_AnotherTest.php';

// PHP Fatal error:  Cannot use bar\Test as Test because the name is already in use in /home/fivestar/phpfuck/foo/AnotherTest.php on line 3