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Troubleshooting Common Loco Translate Errors: From PHP Version Conflicts to Translation Formatting

76 threads Sep 16, 2025 Plugin → Loco translate

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Why Loco Translate Might Throw Errors on Your WordPress Site

Loco Translate is a powerful tool for managing WordPress translations, but like any complex plugin, it can sometimes conflict with your site's environment or other code. Based on community reports, many common errors are not direct bugs in the plugin but are instead caused by underlying server configurations, PHP versions, or malformed translation files. This guide will help you diagnose and resolve the most frequently encountered issues.

1. PHP Version and Extension Conflicts

Many critical errors arise from using outdated or incompatible PHP versions or missing extensions.

  • Problem: Errors like Uncaught Error: Typed property DOMDocument::$documentElement must not be accessed before initialization or Call to undefined function mb_detect_encoding().
  • Cause: The first error can occur in specific PHP runtime environments (often older PHP 8.x versions). The second error means the required mbstring PHP extension is not installed or enabled on your server.
  • Solution:
    • Upgrade your PHP version to a stable, supported release (e.g., 8.3.9 resolved one user's issue).
    • Contact your hosting provider to ensure the mbstring and DOM PHP extensions are installed and activated.
    • Test using a default theme (like Twenty Twenty-Four) and only Loco Translate active to confirm the environment is the cause.

2. The "Blank response from server" / AJAX Error

This is a common but vague error that can have multiple causes.

  • Problem: Actions like Save or Sync fail with a "Blank response from server" message. Browser console may show errors like ERR_HTTP2_PROTOCOL_ERROR or unrelated WebSocket failures.
  • Cause: This is typically a server configuration issue, often related to aggressive caching, security modules (e.g., ModSecurity), or opcode caching (OPcache). In one case, WP Rocket was identified as the culprit.
  • Solution:
    • Temporarily disable all caching (page, browser, opcode) and retry the action. If it works, re-enable caches one by one to identify the conflict.
    • For hosting-level caching or security rules, you may need to contact your hosting provider's support and provide the exact error and AJAX request that is failing.
    • Check that your server's max_input_vars PHP setting is sufficiently high (e.g., 3000+) if you are syncing a very large number of strings.

3. "Unknown format specifier" and "Too few arguments" Errors (The Most Common Issue)

This is, by far, the most prevalent category of error encountered by users.

  • Problem: Fatal errors such as ValueError: Unknown format specifier " ", ArgumentCountError: 3 arguments are required, 2 given, or sprintf(): Too few arguments. These often cause a "Critical Error" on the site or white screens, especially after upgrading to PHP 8.x.
  • Cause: This is NOT a bug in Loco Translate. The error is thrown by a function like sprintf() in your theme or another plugin (common culprits include WooCommerce, WooCommerce Memberships, and various themes). The error occurs because a translation string contains a placeholder (e.g., %s, %d) but the translated version does not use the same number of placeholders correctly. PHP 7.x often ignored these mistakes, but PHP 8.x catches them and throws a fatal error.
  • Solution:
    • Find the faulty translation: The error stack trace will point to the file causing the problem (e.g., /plugins/woocommerce/includes/class-wc-post-types.php). The line number will show the function call, but the bad string is in a translation file (.po or .mo).
    • Use Loco Translate's editor to find the translation for the original string shown in the error. The plugin has a built-in syntax checker that can help identify mismatched placeholders.
    • Fix the translation: Ensure the number and type of placeholders in the translated string exactly match the original. For example, if the original is "All %s", the translation must also have one %s (e.g., "Alle %s" for German, not "Alle %" or "Alle").
    • If the error only happens when Loco Translate is active, it's likely because you are using a custom translation file created by Loco Translate that contains the error, instead of the default theme/plugin file.

4. Installation and File Corruption Issues

  • Problem: Errors on installation or activation, such as Failed opening required '.../lib/compiled/locales.php' or calls to undefined functions like loco_parse_wp_locale().
  • Cause: An incomplete plugin update or corrupted file download.
  • Solution:
    • Fully delete the /loco-translate/ directory from your /wp-content/plugins/ folder via FTP or your host's file manager.
    • Re-install a fresh copy of the plugin directly from the WordPress Plugin Directory.

General Troubleshooting Steps

  1. Enable Debugging: Add define( 'WP_DEBUG', true ); and define( 'WP_DEBUG_LOG', true ); to your wp-config.php file. This will log all errors to /wp-content/debug.log, providing the precise error message and stack trace needed for diagnosis.
  2. Conflict Test: Temporarily switch to a default WordPress theme (Twenty Twenty-Four) and disable all other plugins. If the error stops, reactivate your theme and plugins one by one to find the conflict.
  3. Check Your Logs: Always check your PHP error log and WordPress debug log first. The answer is almost always there.

Remember, the Loco Translate team actively maintains the plugin and tests it across multiple PHP versions. If you encounter an error, providing the full error message and stack trace from your logs is the fastest way to get help from the community or for the developers to identify a genuine bug.

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