compare version using PHP_VERSION_ID

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        | 

To let opcode caches optimize cached code, the `PHP_VERSION_ID`
constant is used to detect the current PHP version instead of calling
`version_compare()` with `PHP_VERSION`.