Description:
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The following code works fine, but produces a PHP notice on PHP 5.2.17.

Strict Standards: Non-static method a::b() cannot be called statically

In the documentation for is_callable there is no mention of the possible strict 
mode notice. There is no notice in PHP 5.3, but I think the change in behaviour 
should be documented. 

Test script:
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error_reporting(E_ALL| E_STRICT);
is_callable(array('a', 'b'));
class a { function b() {} }
exit;