How Can I Effectively Use PDO in PHP to Handle Database Queries and Errors?

Reference: Common PDO Questions

What is PDO?

PHP Data Objects (PDO) is a database abstraction layer in PHP that provides a consistent and portable interface for accessing various database systems.

Frequently Asked Questions

1. PDO Query Fails but No Error Message

To display database errors, set the PDO error mode to exceptions:

$dsn = "mysql:host=$host;dbname=$db;charset=utf8";
$opt = [
    PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION
];
$pdo = new PDO($dsn, $user, $pass, $opt);

Use try-catch blocks to handle errors gracefully or define a custom error handler for more control.

2. Prepared Statements with LIKE Operator

Use placeholders for the search term and escape the LIKE operator using PDO::quote(). For example:

$stmt = $pdo->prepare("SELECT * FROM users WHERE name LIKE ?");
$stmt->execute(['%search_term%']);

3. Prepared Statements for IN () Operator

Create an array of values and pass it as a second parameter to bindParam():

$values = [1, 2, 3];
$stmt = $pdo->prepare("SELECT * FROM users WHERE id IN (?)");
$stmt->bindParam(1, $values, PDO::PARAM_INT, count($values));
$stmt->execute();

4. Binding Identifiers or Keywords

Prepared statements cannot be used to bind identifiers or keywords. Use normal PDO methods, such as PDO::quote(), to escape and protect these values.

5. PDO Prepared Statement in LIMIT Statement

$stmt = $pdo->prepare("SELECT * FROM users ORDER BY id LIMIT ?");
$stmt->bindParam(1, $limit, PDO::PARAM_INT);
$stmt->execute([$limit]);

Remember that displaying error messages without try-catch blocks is not recommended, as it may reveal sensitive information and confuse users.

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