How Can I Efficiently Use the Same Parameter Multiple Times in a PDO Prepared Statement?

Reusing Parameters in PDO Prepared Statements: A Clean Solution

Prepared statements in PDO typically restrict the reuse of the same named parameter. This limitation poses challenges when constructing queries with multiple matching criteria using identical parameters. Manually renaming parameters (:term1, :term2, etc.) is cumbersome and prone to errors.

Leveraging MySQL User-Defined Variables

A more efficient and readable approach involves MySQL's User-Defined Variables. This method streamlines parameter management and enhances code maintainability.

The process involves these steps:

1. Variable Initialization: Use PDOStatement::bindParam to assign a value to a user-defined variable.

    $stmt = $dbh->prepare("SET @term = :term");
    $stmt->bindParam(":term", "%$term%", PDO::PARAM_STR);

2. Query Integration: Substitute multiple instances of the original parameter with the user-defined variable (@term) in your SQL query.

    SELECT ... FROM table WHERE name LIKE @term OR number LIKE @term

3. Statement Execution: Prepare and execute the modified query.

    $stmt = $dbh->prepare($sql);
    $stmt->execute();

Illustrative Example:

Consider this complex query:

(
    SELECT
        t1.`name` AS resultText
    FROM table1 AS t1
    WHERE
        t1.parent = :userID
        AND
        (
            t1.`name` LIKE :term
            OR
            t1.`number` LIKE :term
            AND
            t1.`status` = :flagStatus
        )
)
UNION
(
    SELECT
        t2.`name` AS resultText
    FROM table2 AS t2
    WHERE
        t2.parent = :userParentID
        AND
        (
            t2.`name` LIKE :term
            OR
            t2.`ticket` LIKE :term
            AND
            t1.`state` = :flagTicket
        )
)

Refactoring with User-Defined Variables yields:

SET @term = :term;

(
    SELECT
        t1.`name` AS resultText
    FROM table1 AS t1
    WHERE
        t1.parent = :userID
        AND
        (
            t1.`name` LIKE @term
            OR
            t1.`number` LIKE @term
            AND
            t1.`status` = :flagStatus
        )
)
UNION
(
    SELECT
        t2.`name` AS resultText
    FROM table2 AS t2
    WHERE
        t2.parent = :userParentID
        AND
        (
            t2.`name` LIKE @term
            OR
            t2.`ticket` LIKE @term
            AND
            t1.`state` = :flagTicket
        )
)

Advantages of this Approach:

• Conciseness: Avoids repetitive parameter naming.
• Clarity: Improves code readability and maintainability.
• Modularity: Encapsulates parameter handling, simplifying query management.

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