This function returns an array of the names of the declared classes in the current
script.
Note: In PHP 4.0.1pl2, three extra classes are returned at the beginning of the array:
stdClass (defined in Zend/zend.c), OverloadedTestClass (defined in
ext/standard/basic_functions.c) and Directory (defined in
ext/standard/dir.c).
Also note that depending on what libraries you have compiled into PHP, additional classes
could be present.
