A regex solution:
<?php
$str = "ckb=199&ckb=232&ckb=200&ckb=233&ckb=201&ckb=234";
preg_match_all("/=([^&]+|.*$)/", $str, $matches);
print_r($matches[1]);
?>
Output:
Array
(
[0] => 199
[1] => 232
[2] => 200
[3] => 233
[4] => 201
[5] => 234
)
solved Split PHP Variable in to array?