Resolving common PHP upgrade issues

When upgrading PHP versions on ruachost.com, you may encounter compatibility problems with existing scripts or applications. This guide outlines common issues and how to resolve them.

Why Issues Occur

Deprecated functions: Older PHP versions may use functions removed in newer releases.
Changed default settings: Configuration directives may behave differently.
Extension compatibility: Some extensions are no longer bundled or require manual installation.
Syntax changes: Certain language constructs are updated or removed.

Common Issues and Fixes

1. Deprecated or Removed Functions

Functions like mysql_connect() are removed in PHP 7+.

Fix: Replace with mysqli or PDO.

// Old
$conn = mysql_connect("localhost", "user", "pass");

// New
$conn = new mysqli("localhost", "user", "pass", "database");

2. Short Tags Disabled

Some servers disable <? ?> short tags.
Fix: Use full tags <?php ?> or enable short tags in php.ini.

3. Extension Changes

Extensions like mcrypt are removed in PHP 7.2+.
Fix: Use openssl or sodium for encryption.

4. Error Handling Differences

set_error_handler() behavior may differ.
Fix: Update error handling code to match new standards.

5. Default Charset

PHP 5.6+ defaults to UTF‑8.
Fix: Ensure your database and scripts use consistent encoding (utf8mb4).

6. Session Handling

Session storage paths may change.
Fix: Verify session.save_path in php.ini and adjust permissions.

7. Strict Variable Handling

PHP 7 introduces stricter type checks.
Fix: Update code to match expected types or use type declarations.