PHP Version Support Matrix
From WHMCS Documentation
| WHMCS Version (Status) | PHP v5.2 | PHP v5.3 | PHP v5.4 | PHP v5.6 | PHP v7.0 | PHP v7.1 | PHP v7.2 | PHP v7.3 |
|---|---|---|---|---|---|---|---|---|
| v6.3 (EOL) | Y | Y | Y | Y | N | N | N | N |
| v7.0 (EOL) | N | N | N | Y | Y | N | N | N |
| v7.1 (EOL) | N | N | N | Y | Y | N | N | N |
| v7.2 (EOL) | N | N | N | Y | Y | N | N | N |
| v7.3 (EOL) | N | N | N | Y | Y | N | N | N |
| v7.4 (EOL) | N | N | N | Y | Y | N | N | N |
| v7.5 (LTS) | N | N | N | Y | Y | Y | Y | N |
| v7.6 (Active) | N | N | N | Y | Y | Y | Y | N |
| v7.7 (Beta) | N | N | N | Y | Y | Y | Y | N |