What does the error message "Invalid parameter number" in the registration form mean, specifically in relation to the mismatch of bound variables and tokens?

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The error message "Invalid parameter number" in the registration form suggests that there is a mismatch between the number of bound variables and the number of tokens used in the query. This error commonly occurs in prepared statements, where placeholders are used for safe insertion of values into SQL queries. The mismatched number of placeholders and parameters can cause the query execution to fail, resulting in the error message. To resolve the issue, the correct number of bound variables and tokens must be matched according to the query requirements.