Why Does Inserting 0 into a BIT(1) Field in MySQL using PDO Result in 1?

Understanding Value Insertion Issues in Bit(1) Fields

Database programming using PHP's PDO extension can present challenges when handling data manipulation, especially with binary data types like bit(1). This article explores a common issue encountered when inserting a value of 0 into a bit(1) field, resulting in an unexpected value in the database.

Problem Statement

Inserting a value of 0 into a bit(1) field using PDO prepared statements yields a stored value of 1. This discrepancy occurs when using placeholder (?), named placeholder (:placeholder), bindValue(), and bindParam() methods. Querying the database directly using the SQL statement without placeholders inserts the correct value of 0.

Solution

The recommended solution is to modify the field type from bit(1) to TINYINT(1). BIT data types can cause compatibility issues with client libraries, including PDO. It's important to use TINYINT(1) instead of BIT(1) for storing boolean values to avoid such problems.

Alternative Solution for BIT(1)

If changing the field type is not feasible, using the bindValue() method with the PDO::PARAM_INT type hint can resolve the issue. The following code snippet demonstrates this:

<code class="php">$pdo = new PDO("connection string etc");
$statement = $pdo->prepare('INSERT INTO `test` (SomeText,TestBool) VALUES (:someText,:testBool)');
$statement->bindValue(':someText', "TEST");
$statement->bindValue(':testBool', 0, PDO::PARAM_INT);
$statement->execute();</code>

Takeaway

Using TINYINT(1) is the preferred method for storing boolean values in a MySQL database. However, if BIT(1) must be used, the bindValue() method with the PDO::PARAM_INT type hint can resolve the issue of inserting 0 values. It's important to note that BIT data types may cause incompatibility with certain client libraries and should be used cautiously.

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