What best practices should be followed when handling database queries and output in PHP to avoid errors like the ones described in the forum thread?

The best practices for handling database queries and output in PHP to avoid errors include using prepared statements to prevent SQL injection attacks, validating user input before executing queries, and properly escaping output to prevent XSS attacks. It is also important to handle errors gracefully by using try-catch blocks and displaying informative error messages to users. 

// Example of using prepared statements to prevent SQL injection

// Establish database connection
$pdo = new PDO("mysql:host=localhost;dbname=mydatabase", "username", "password");

// Prepare a SQL statement with a placeholder
$stmt = $pdo->prepare("SELECT * FROM users WHERE username = :username");

// Bind parameters to the placeholder
$stmt->bindParam(':username', $_POST['username']);

// Execute the query
$stmt->execute();

// Fetch the results
$results = $stmt->fetchAll();

// Output the results
foreach ($results as $row) {
    echo htmlentities($row['username']);
}

Keywords

SQL injection prepared statements PDO error handling data validation

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