| Detection Method | How It Works | PHP Checker Evasion (Often Fails) | |----------------|--------------|------------------------------------| | | Many attempts from same IP in short time | Proxy rotation – but proxies get blacklisted | | BIN Mismatch | Card BIN says USA, but checkout IP is Vietnam | Proxy matching BIN country – adds latency | | Low-Value Auth Pattern | Repeated $0.50 or $1.00 charges | Randomize amounts ($0.10 to $4.99) | | TLS Fingerprinting (JA3) | cURL TLS handshake is distinct from browsers | Hard to change without custom OpenSSL compilation | | Missing Browser Assets | No CSS/JS/image requests | Some PHP checkers pre-fetch assets via cURL | | Card Testing Pattern | Same card attempted on 10+ gateways in 5 min | Use fewer gateways per card (less efficient for criminals) | | Behavioral Analytics | No mouse movements, no keystroke timing | Impossible to simulate accurately in PHP |

To consume this script via AJAX in a frontend checkout form, expose the logic through a secure PHP API endpoint. Save the file below as validate.php .