升级PHP 7后WordPress中WooCommerce加入购物车功能失效求助

Hey Kunal, let's work through this WooCommerce issue you're facing after upgrading to PHP 7. I've seen this kind of compatibility problem a lot, so here's a step-by-step guide to fix it:

1. Verify WooCommerce Version Compatibility #

First, check if your installed WooCommerce version supports both PHP 7 and WordPress 5.1.1. WordPress 5.1.1 (released in 2019) works best with WooCommerce versions 3.3.x to 3.6.x—older versions (pre-3.0) don’t support PHP 7 at all, and newer WooCommerce releases (3.7+) require a newer WordPress version.

If your WooCommerce is outdated, you’ll need to upgrade it to a compatible version. Always backup your site and database before upgrading!

2. Enable WordPress Debug Mode to Get Specific Errors #

The "This page is not working" message is too vague. Let’s turn on debug logging to see exactly what’s breaking:

• Access your site’s root directory via FTP or cPanel File Manager.
• Open wp-config.php and find the line that says define('WP_DEBUG', false);
• Change it to:

  define('WP_DEBUG', true);
  define('WP_DEBUG_LOG', true);
  define('WP_DEBUG_DISPLAY', false);
  

• Save the file, then try clicking the Add to Cart button again.
• Check the wp-content/debug.log file for detailed error messages (e.g., deprecated functions, syntax errors, or fatal errors). This will point you directly to the problem (a plugin, theme, or custom code snippet).

3. Test for Plugin Conflicts #

Third-party plugins often cause compatibility issues after PHP upgrades:

• Deactivate all plugins except WooCommerce.
• Test the Add to Cart functionality. If it works, reactivate plugins one by one, testing after each activation.
• When the issue reappears, you’ve found the conflicting plugin. Either update that plugin to its latest PHP 7-compatible version, or replace it with an alternative.

4. Check Theme Compatibility #

Your custom theme might use PHP 5.6-specific syntax that breaks in PHP 7:

• Switch to a default WordPress theme like Twenty Nineteen (the default theme for WP 5.1.1).
• Test Add to Cart again. If it works, your theme is the problem.
• To fix the theme:
  • Look for deprecated PHP functions (e.g., mysql_* instead of mysqli_* or PDO).
  • Check for outdated syntax like $var = &new Class(); (remove the &—PHP 7 no longer supports reference assignments for new objects).
  • Ensure array keys are quoted (e.g., $arr['key'] instead of $arr[key]—PHP 7 treats unquoted keys as constants, which throws errors).
  • If you’re not comfortable editing code, contact the theme developer for a PHP 7-compatible update.

5. Review Server PHP Error Logs #

If WP debug logs don’t show anything, check your server’s PHP error logs. Most hosting providers let you access these via cPanel (look for "Error Log" in the metrics section) or your hosting dashboard. These logs will show server-level errors that might not appear in WP’s debug log.

6. Consider Upgrading WordPress (Carefully) #

WordPress 5.1.1 is quite old, and newer versions have better PHP 7 compatibility. If you’re able to upgrade:

• Backup your site and database first (this is non-negotiable).
• Upgrade WordPress to version 5.6.x (the latest version that still supports PHP 7.0-7.4 and is compatible with older WooCommerce versions).
• After upgrading WP, update WooCommerce to the latest version compatible with WP 5.6.x. This will resolve most compatibility gaps between PHP 7, WP, and WooCommerce.

内容的提问来源于stack exchange，提问作者kunal