trim from first and last of string how do it [duplicate]

This question already has answers here: Closed 12 years ago.

Possible Duplicate:

unset last item of array

i want do this without of expload, array_pop and array_shift

$item[$fieldneedle] = " node_os_disk_danger ";
$objectName = preg_split('/_/',$item开发者_Go百科[$fieldneedle]);
$objectName == "os_disk";

in this example i need os_disk

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/(?:^.*?_)(.*)(?:_.*$)/

..will only capture the os_disk part