Why Does `bindParam` Fail with Constant Values in PDO, and How Can I Fix It?

Troubleshooting "Cannot Pass Parameter by Reference" Error in bindParam

When utilizing bindParam with a constant value like null or empty strings, you may encounter this perplexing error. The culprit lies in the fundamental difference between bindParam and bindValue.

bindParam vs. bindValue

bindParam expects a variable parameter passed by reference, while bindValue directly assigns a value to a placeholder. This distinction becomes critical when working with constant values.

Solution: Use bindValue

To resolve the error, replace bindParam with bindValue. For null values, use the following syntax:

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

Note:

Attempting to bind a null value using bindParam with PDO::PARAM_NULL may not work for all users. bindValue has proven to be a more reliable solution.

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