<?php function spool_status() {
    return [
        'Waiting', 
        'Manufacturing', 
        'QC', 
        'Paint', 
        'Completed'
    ];
} 

function rollback_spool_status() {
    return [
        'QC', 
        'Paint', 
        'Completed'
    ];
} 
function spool_status_prev($status) {
    $spool_status = rollback_spool_status(); 
    $status_index = array_search($status, $spool_status); 

    if ($status_index > 0) {
        $previous_status = $spool_status[$status_index - 1];
        return $previous_status;
    } else {
        return $status;
    }
}
?>