Description:
------------
If you pass an invalid array as a callback (for example if your object is actually just NULL), call_user_func_array warns with a message that implies that arrays are not valid callbacks:

Warning: call_user_func_array(): First argument is expected to be a valid callback, 'Array' was given in ...

This is misleading.  Perhaps the wording should be changed to match call_user_func's warning:

Warning: call_user_func(Array): First argument is expected to be a valid callback in ...

Alternatively the error message can be made more specific when passed an array as to where in the trail of objects the call failed (and possibly what the value/type was).

Reproduce code:
---------------
<?php
$foo = NULL;
call_user_func_array(array($foo, 'foofunc'), array($var1));
call_user_func(array($foo, 'foofunc'), $var1);
?>