test: fix backward compatibility breaking for php < 5.5
test: fix backward compatibility breaking for php < 5.5

PHP Parse error:  syntax error, unexpected 'class' (T_CLASS)

http://php.net/manual/en/language.oop5.basic.php#language.oop5.basic.class.class
```
::class
Since PHP 5.5, the class keyword is also used for class name resolution.
```

hprose/hprose-php