The credit card library allows plausability checking credit cards before submitting them to a payment processor. The best practices at time of writing from writing as determined by stack overflow are used, and the class is designed to be as hassle-free as possible so it can be used in a wide variety of environments.
Usage:
// Initialize
$c = new Altruja\CreditCard("4200000000000000");
// Detect type
echo $c->type(); // "visa"
// Verify checksum
echo $c->valid(); // true