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Resolving the 'Cannot declare class OCDI_Plugin' Fatal Error

17 threads Sep 10, 2025 Plugin → One click demo import

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One of the most common and disruptive errors users encounter with the One Click Demo Import plugin is the activation fatal error: Fatal error: Cannot declare class OCDI_Plugin, because the name is already in use. This error halts the plugin's activation and prevents you from importing your demo content. This guide will explain why this conflict happens and walk you through the steps to resolve it.

Why This Error Occurs

This error is a PHP class naming conflict. It means that the code for the OCDI_Plugin class is being declared twice. Based on numerous community reports, this is almost never a bug within the standalone One Click Demo Import plugin itself. Instead, it is a conflict caused by one of two scenarios:

  1. Theme Bundling: Many themes bundle the core OCDI plugin code directly within their own files to offer built-in demo import functionality. When you then try to install the separate OCDI plugin, the two copies of the same class conflict with each other.
  2. Plugin Conflict: In rarer cases, another plugin on your site might also be bundling this code, leading to the same conflict.

How to Fix the 'Cannot declare class OCDI_Plugin' Error

Follow these troubleshooting steps to identify and resolve the conflict.

Step 1: Check Your Theme's Documentation

Before doing anything else, review your theme's documentation. Most modern themes that include demo import functionality will specify whether they bundle the OCDI tool. If they do, they will almost always instruct you not to install the separate plugin. The theme's built-in importer is all you need.

Step 2: Deactivate the Standalone OCDI Plugin

If your theme bundles OCDI, you simply need to deactivate and delete the standalone One Click Demo Import plugin. Your theme's import options, typically found under Appearance > Import Demo Data, should then work without any issues.

Step 3: Identify the Conflict (If Your Theme Doesn't Bundle OCDI)

If you've confirmed your theme does not include OCDI, the conflict is likely with another plugin. To find the culprit, you need to perform a conflict test.

  1. Deactivate all your plugins except for One Click Demo Import.
  2. Try to activate OCDI. If it activates successfully, you know a plugin was causing the issue.
  3. Reactivate your other plugins one by one, checking after each activation to see if the error returns. The last plugin you activated before the error reappears is the source of the conflict.

Step 4: Contact the Author of the Conflicting Software

Once you identify whether the conflict is with your theme or another plugin, your next step is to contact their support team. Politely inform them that their product is bundling the OCDI_Plugin class, which is causing a fatal error when users try to run the standalone OCDI plugin. They should be able to provide a fix or an update that resolves the namespace conflict.

Summary and Final Thoughts

The Cannot declare class OCDI_Plugin error is a classic case of duplicate code. The solution almost always involves deactivating the redundant plugin and using the importer provided by your theme. Remember, the standalone One Click Demo Import plugin is designed for theme developers to integrate into their products; most end-users will use it through their theme's interface, not as a separate plugin.

By following these steps, you should be able to resolve the conflict and get back to importing your demo content.

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