Description:
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The addServers() call causes a crash if the server elements in the array have any other keys than 0, 1 or 2. 



Reproduce code:
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<?php

$servers = array ( 0 => array ( 'KEYHERE' => 'localhost', 11211, 3 ), );

$m = new memcached();

$m->addServers($servers);

Expected result:
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Servers are added succesfully.

Actual result:
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Segmentation fault. Probably happens in php_memcached.c:1400