Super simple example of how to implement a system that can handle multiple types of fraud checks

gistfile1.php

<?php

/*
* Fraud levels:
* 0 - no fraud
* 1 - needs to be reviewed
* 2 - denied
*/

// Set the initial fraud status to zero
$fraud_status = 0;

// Loop thru our fraud checks
foreach($fraud_checks as $check) {
    // Run the check
    $check_status = $check->run();

    // Elevate the fraud status, if needed
    if($check_status > $fraud_status)
        $fraud_status = $check_status

    // Don't waste time running more checks if we already know its fraud
    if($check_status === 2)
        break;
}