How Can I Reuse Bound Parameters Multiple Times in a Prepared Statement?

Use Bound Parameters Multiple Times

In database programming, using bound parameters is crucial for preventing SQL injection attacks. However, developers often encounter an issue when trying to use the same parameter multiple times within a prepared statement.

Original Problem Statement

The original post discusses a scenario where a user wishes to implement a search engine that utilizes a UNION SELECT to fetch data from different tables, each with a different search criteria. The query contains several instances of a ":term" parameter, which is being bound to a prepared statement.

Solution: User-Defined Variables

The provided solution offers an alternative approach to using bound parameters multiple times. By utilizing MySQL User-Defined Variables, developers can simplify their code and improve readability:

1. Initialize the Variable: Create a MySQL User-Defined Variable and assign it the desired value.
2. Utilize the Variable: Reference the User-Defined Variable within your query, where you would have otherwise used ":term" multiple times.

Example Code

$sql = "SET @term = :term";

$stmt = $dbh->prepare($sql);
$stmt->bindValue(":term", "%$term%", PDO::PARAM_STR);
$stmt->execute();

$sql = "SELECT ... FROM table WHERE name LIKE @term OR number LIKE @term";

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

Advantages

• Improved code readability
• Reduced need for additional PHP functions
• No worries about parameter name conflicts

Downsides

• Requires an additional MySQL query

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