What are common mistakes when outputting data from a database in an HTML form using PHP?

Common mistakes when outputting data from a database in an HTML form using PHP include not properly escaping the data to prevent SQL injection attacks and not encoding special characters to prevent HTML injection attacks. To solve this issue, always use prepared statements to interact with the database and htmlspecialchars() function to encode special characters when displaying data in HTML forms. 

// Retrieve data from the database
$stmt = $pdo->prepare("SELECT * FROM users WHERE id = ?");
$stmt->execute([$userId]);
$user = $stmt->fetch();

// Output the data in an HTML form
<input type="text" name="username" value="<?php echo htmlspecialchars($user['username']); ?>">
<input type="email" name="email" value="<?php echo htmlspecialchars($user['email']); ?>">

Keywords

SQL injection htmlentities prepared statements XSS attacks data validation

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