Cross-Version Compatibility Testing

TL;DR

Explanation

Strategies: (1) GitHub Actions matrix: [php: ['8.1','8.2','8.3']] runs tests against each version. (2) PHPStan with phpCompatibilityFixer to detect usage of features not available in minimum PHP version. (3) composer check-platform-reqs validates extension requirements. (4) phpenv or phpbrew to switch PHP versions locally. (5) Docker: test against official php:8.x-cli images. (6) PHPCompatibility (PHPCS sniff): checks code against target PHP version. Key: declare minimum PHP version in composer.json require->php field and enforce with tooling.

Common Misconception

Why It Matters

Common Mistakes

• Only testing against one PHP version in CI.
• Not specifying minimum PHP version in composer.json.
• Not using PHPCompatibility PHPCS sniffs to catch API usage differences.

Code Examples

# composer.json — no PHP version constraint:
{
    "require": {
        "php": "*"
    }
}

# composer.json:
{
    "require": {
        "php": ">=8.1"
    }
}

# GitHub Actions:
matrix:
  php: ['8.1', '8.2', '8.3']

# phpcs.xml:
<rule ref="PHPCompatibility"/>
<config name="testVersion" value="8.1-"/>

References

• ↗ https://github.com/PHPCompatibility/PHPCompatibility

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