Migrating from PHP 7.4 to PHP 8.0

Migrating PHP 7.4 to 8.0 requires testing union types, changed comparisons and stricter errors.

What It Does

Migrating PHP 7.4 to 8.0 requires testing union types, changed comparisons and stricter errors. The following examples distinguish a normal use case, a boundary case and a practical application.

Requirements and Compatibility

A staging runtime matching the target PHP release and a regression test suite.

PHP 8.0 introduced union types, named arguments, match, nullsafe access and several behavior changes. Test syntax against the intended runtime.

The code focuses on the core concept. Production implementation may also need routes, validation, persistence, authorization or deployment tooling.

Example 1: Basic Behavior

Union types are available starting with PHP 8.0, not PHP 7.4.

<?php
function displayKey(int|string $value): string { return (string) $value; }
echo displayKey("SKU-4");

Example 2: Another Case

Changed argument validation now throws TypeError or ValueError in many APIs.

<?php
try { strlen([]); } catch (TypeError $e) { echo "TypeError"; }

Practical Example: Putting It to Use

Use strict match expressions deliberately when modernizing switch-based code.

<?php
$value = "9";
echo match ($value) { 9 => "integer", "9" => "string", default => "other" };

Important Behavior and Edge Cases

TypeError/ValueError behavior and compatibility changes can break code formerly accepted.

Comparison with Related Functions or Approaches

Common Beginner Mistakes

Key Takeaways

• Migrating PHP 7.4 to 8.0 requires testing union types, changed comparisons and stricter errors.
• TypeError/ValueError behavior and compatibility changes can break code formerly accepted.
• Run the existing test suite against both runtimes before deployment.

Before adapting these examples, verify the return values, test the failure paths and confirm that your application meets its security and environment requirements.