Troubleshooting Common Post Types Order Plugin Errors: Missing Arguments, SQL Syntax, and Headers

The Post Types Order plugin is a popular tool for managing the sequence of posts and custom post types in WordPress. However, like any complex software, it can sometimes conflict with other code, leading to errors. Based on community reports, this guide addresses the most frequent issues and provides steps to resolve them.

1. Warning: Missing argument 2 for wpdb::prepare()

This is one of the most common errors reported. It occurs when the plugin code calls the wpdb::prepare() function without providing the required number of arguments for a secure SQL query.

Why it happens:

The wpdb::prepare() method is a WordPress function used to safely prepare SQL queries. It requires at least two arguments: the SQL query string and the values to be sanitized and inserted into the query. An error is thrown if the function is called without these necessary values, often due to a coding oversight in a plugin update.

How to fix it:

This error was acknowledged and fixed by the Post Types Order team in a specific update (version 1.8.9.1). The first step is always to ensure you are running the latest version of the plugin. If you are up-to-date and still see the error, it may be a regression or a conflict.

2. SQL Syntax Errors (e.g., near ')')

Users often report SQL syntax errors showing up in Apache logs or on the frontend, particularly mentioning a problem near a closing parenthesis ).

Why it happens:

These errors are typically not caused by the Post Types Order plugin's core functionality but are triggered by how it interacts with other code. The error often originates from a separate theme or plugin function that is building a query with an IN () clause. This clause is meant to contain a list of term IDs, but if the list is empty, it results in invalid SQL (IN ()). The Post Types Order plugin's sorting mechanism then interacts with this malformed query, making it appear as the source.

How to fix it:

• Identify the Culprit: The error message usually includes a call stack. Look for the theme or plugin function that is creating the query with the empty IN () clause. Common culprits are navigation functions, category-related widgets, or other plugins that filter posts by taxonomy terms.
• Fix the Code: The theme or plugin code generating the query needs to be modified to check if the list of term IDs is empty before building the SQL query. If the list is empty, the query should be handled differently or abandoned.
• Temporary Workaround: If you cannot fix the source code immediately, you may need to temporarily disable the problematic theme function or widget causing the empty query.

3. Warning: Cannot modify header information - headers already sent

This error prevents WordPress from redirecting users after saving settings or updating a post, often showing a broken page instead.

Why it happens:

HTTP headers must be sent before any content (HTML, whitespace, text). This error occurs when something—often an unintended echo statement, warning, or even a blank space—is outputted before the WordPress functions try to send headers for a redirect. In one instance, an echo statement in the plugin's class.options.php file was identified as the cause.

How to fix it:

• Check for Plugin Updates: The Post Types Order team has likely addressed such issues in subsequent updates.
• Enable Debugging: Add define('WP_DEBUG', true); to your wp-config.php file to make all warnings and notices visible. This can help identify the exact file and line number where the premature output is starting.
• Inspect the Code: If the debug log points to a file in the Post Types Order plugin (like class.options.php), you may need to edit that file to remove the unnecessary output, but this is not recommended as it will be overwritten on update. The better solution is to report the issue and wait for an official patch.

4. Unknown column 'status' in 'where clause'

This error references a database column that does not exist.

Why it happens:

This is a clear example of a conflict. The error is caused by custom code from a theme or another plugin that is incorrectly trying to query a column named status in the wp_posts table. The correct column name is post_status. The Post Types Order plugin's sorting function interacts with this flawed query, surfacing the error.

How to fix it:

You must locate and correct the custom code that uses status = 'pending' (or similar) in its SQL query. The code should be updated to use the correct column name, post_status.

General Troubleshooting Steps

1. Update Everything: Always ensure WordPress, your theme, and all plugins (especially Post Types Order) are updated to their latest versions. Many bugs are patched in new releases.
2. Conflict Test: Disable all other plugins and switch to a default WordPress theme (like Twenty Twenty-One). If the error disappears, reactivate your plugins and theme one by one to identify the source of the conflict.
3. Check Error Logs: Your server's PHP and Apache error logs provide detailed information that is crucial for diagnosing these problems. The error message and stack trace will often point directly to the problematic file.

Remember, while the Post Types Order plugin can surface these errors, the root cause often lies in a conflict with other code. Isolating and fixing that underlying code is the most permanent solution.