Use array_search to get the key and remove it with unset if found:
if (($key = array_search('strawberry', $array)) !== false) {
unset($array[$key]);
}
array_search returns false (null until PHP 4.2.0) if no item has been found.
And if there can be multiple items with the same value, you can use array_keys to get the keys to all items:
foreach (array_keys($array, 'strawberry') as $key) {
unset($array[$key]);
}