How to Resolve PDO Error: SQLSTATE[HY000]: General Error: 2031 When Using Placeholders?

PDO Error: Understanding and Resolving SQLSTATE[HY000]: General Error: 2031

When encountering the error "PDO error: SQLSTATE[HY000]: General error: 2031" while attempting to execute SQL statements with placeholders, it's crucial to delve into the underlying issue. This error often arises when an excessive number of parameters are bound to a statement.

In your specific case, while the bindValue() method is used to manually add LIMIT placeholders, it's important to note that each bindValue() call associates a value with a specific parameter name. If two or more calls are made with the same parameter name, the error 2031 will be triggered.

To resolve this, ensure that each bindValue() call uses a unique parameter name. For example:

<code class="php">$sth->bindValue(':page_offset', $page - 1, PDO::PARAM_INT);
$sth->bindValue(':entries_per_page', $page * $entries_per_page, PDO::PARAM_INT);</code>

Alternatively, consider using PDO's positional binding syntax, where parameters are numbered instead of named. This can eliminate the risk of binding multiple values to the same parameter:

<code class="php">$sth->execute([$page - 1, $page * $entries_per_page]);</code>

Remember, when working with prepared statements, it's essential to ensure that the number of bound values matches the number of placeholders in the SQL statement. This helps prevent ambiguity and ensures proper execution of the query.

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