Why Does `mysqli_stmt::bind_result()` Fail When the Number of Bind Variables Doesn't Match the Number of Selected Fields?

Understanding the Error in mysqli_stmt::bind_result()

When working with prepared statements in PHP's MySQLi extension, you may encounter the error "mysqli_stmt::bind_result(): Number of bind variables doesn't match number of fields in prepared statement." This issue occurs when the number of variables expected by your query does not match the number of variables bound to the result.

Analyzing the Provided Code

In the provided code, the issue was with the SELECT statement used to prepare the statement:

$stmt = $mysqli->prepare("SELECT username AND password FROM users WHERE username = ?");

In this statement, the SELECT clause specified two fields, "username" and "password." However, only one bind variable was used ($username):

$stmt->bind_param('s', $username);

Resolving the Issue

To fix the issue, the SELECT clause should be modified to include only the fields that are being bound to the result. In this case, only "username" is needed:

$stmt = $mysqli->prepare("SELECT username FROM users WHERE username = ?");

With this modification, the number of fields in the query will match the number of bind variables, and the error will be resolved.

Additional Notes

• When using multiple bind variables, ensure that there are the same number of bind variables as there are fields in the SELECT clause.
• Double-check that the data types of the bind variables match the corresponding fields.
• If you still encounter the error, try checking the prepared statement using $stmt->error to identify any potential syntax or connection issues.

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