Description:
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PHP does not guarantee any destruction order. This means if you instantiate class 
A before B, A may be destructed before B or B may be destructed before A. As 
AMQPChannel needs an AMQPConnection object for construction one could assume, 
that AMQPChannel objects are always destructed before AMQPConnection objects are 
destructed. This may not always be the case. For cases where the AMQPConnection 
object is destructed before the related AMQPChannel the AMQPConnection destructor 
needs to take care of destructing related AMQPChannel objects. And this is what 
the attached patch does.