Why is it considered bad practice to execute database queries within loops in PHP programming?

Executing database queries within loops in PHP programming is considered bad practice because it can lead to multiple unnecessary connections to the database, which can significantly slow down the performance of the application. Instead, it is recommended to fetch all the required data in a single query and then iterate over the results in the loop. 

// Example of fetching data with a single query and then iterating over the results

// Connect to the database
$pdo = new PDO('mysql:host=localhost;dbname=mydatabase', 'username', 'password');

// Fetch all data in a single query
$stmt = $pdo->query('SELECT * FROM my_table');
$results = $stmt->fetchAll(PDO::FETCH_ASSOC);

// Iterate over the results
foreach ($results as $row) {
    // Process each row
    echo $row['column_name'] . "<br>";
}

Keywords

database queries loops performance SQL injection optimization

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