Description:
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As far as I'm aware, exceptions are not supposed to be thrown by default, but rather errors are supposed to be raised.

Serializing a closure throws an exception, when it should be raising an E_ERROR instead.

Reproduce code:
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<?php

$foo = function() { };

serialize($foo);

Expected result:
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E_ERROR is raised and the script dies.

Actual result:
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An exception is thrown.