The array returned by this function will be in the order the classes were defined / included / required and this order does not appear to change.
For example:
<?PHP
//define classone
class classone { }
//define classtwo
class classtwo { }
//This will show X classes (built-ins, extensions etc) with
//classone and classtwo as the last two elements
print_r(get_declared_classes());
//define classthree
class classthree { }
//...and four
class classfour { }
//Shows the same result as before with class three and four appended
print_r(get_declared_classes());
?>
Output:
Array
(
[0] => stdClass
[1] .... other defined classes....
[10] => classone
[11] => classtwo
)
and...
Array
(
[0] => stdClass
[1] .... other defined classes....
[10] => classone
[11] => classtwo
[12] => classthree
[13] => classfour
)