Why Does `mysqli_stmt::bind_param` Fail When Parameter and Placeholder Counts Mismatch?

Number of Parameters in bind_param Must Match Query Placeholders in mysqli

A common error encountered when using mysqli_stmt::bind_param is the mismatch between the number of parameters provided and the number of placeholders (question marks) in the prepared SQL query. Here's how to ensure they align correctly:

The type definition string in bind_param() consists of a sequence of characters representing the data type of each parameter. Each character in the string must correspond to a single placeholder in the prepared query. For instance:

$stmt->bind_param("sss", $one, $two, $three);

In the above example, the type definition string "sss" contains three 's' characters, indicating that the three parameters ($one, $two, $three) are all strings. The prepared query must then contain three placeholders to match this definition, like:

$stmt->prepare("INSERT INTO table (one, two, three) VALUES (?,?,?)");

If the number of characters in the type definition string does not match the number of placeholders in the query, bind_param() will generate an error stating that the number of variables does not equal the number of placeholders.

To ensure proper execution, always verify that the count of characters in the type definition string matches the count of placeholders in the prepared query.

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