Why Does PDO\'s `bindParam` Fail with Constants and How Can I Fix the \'Cannot pass parameter 2 by reference\' Error?

Troubleshooting "Cannot pass parameter 2 by reference" Error in PDO bindParam

When attempting to execute a prepared statement using PDO's bindParam method, you may encounter an error if you utilize a constant value as the parameter to be bound. This error stems from a fundamental misunderstanding of how bindParam operates.

bindParam expects a variable as its second parameter, allowing you to modify the value passed to the statement at a later time. This is not suitable for constant values, which cannot be modified. To resolve this issue, utilize the bindValue method instead.

Example:

Replace:

$stmt->bindParam(':v1', PDO::PARAM_NULL); 

With:

$stmt->bindValue(':v1', null, PDO::PARAM_INT); 

By using bindValue, you explicitly provide a specific value to the placeholder, eliminating the need for a reference. This resolves the error and allows your statement to execute correctly.

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