Use prepared statements in PHP mainly to prevent SQL injection attacks, improve performance, make the code clearer and easier to debug. 1. It effectively prevents SQL injection through parameterized queries, ensuring that user input is always processed as data rather than SQL logic; 2. Preprocessing statements only need to be compiled once when executed multiple times, significantly improving execution efficiency, especially suitable for batch operations; 3. Parameter binding supports position and named placeholders, separates SQL and data, and enhances code readability and maintenance; 4. Errors can be exposed in advance in the prepare phase, and exceptions can be handled uniformly by setting error mode, which helps to quickly debug.

Use prepared statements in PHP, mainly to execute SQL queries safely and efficiently . Especially when processing user input, prepared statements can effectively prevent SQL injection attacks, while also improving the performance and readability of database operations.

The following is a few practical application scenarios to explain why you should use it.

1. Prevent SQL injection attacks

SQL injection is a common attack method where attackers construct malicious input and tamper with SQL query logic to obtain or modify data you do not want them to touch.

For example:

If you splice SQL queries like this:

 $username = $_POST['username'];
$password = $_POST['password'];
$sql = "SELECT * FROM users WHERE username = '$username' AND password = '$password'";

An attacker can enter ' OR '1'='1 , which causes the query to become:

 SELECT * FROM users WHERE username = '' OR '1'='1' AND password = ''

The result is bypassing login verification.

Using prepared statements:

 $stmt = $pdo->prepare("SELECT * FROM users WHERE username = ? AND password = ?");
$stmt->execute([$username, $password]);

At this time, no matter what the user inputs, it will be processed as a string, which will not affect the structure of SQL and fundamentally prevent injection.

2. Improve performance: more efficient execution after multiple times

prepared statements will be parsed and compiled by the database during the first execution. After execution again, you only need to pass in new parameters, and there is no need to repeatedly parse SQL statements.

This is useful for situations where the same SQL template needs to be executed multiple times, but with different parameters.

For example, batch insertion of data:

 $stmt = $pdo->prepare("INSERT INTO users (name, email) VALUES (?, ?)");
foreach ($users as $user) {
    $stmt->execute([$user['name'], $user['email']]);
}

Compared to splicing SQL strings and executing them each time, this method is more efficient and safer.

3. Parameter binding makes the code clearer

Using parameter binding, you can separate variables and SQL statements to make the code easier to read and maintain.

PHP supports two forms of parameter binding:

• Position placeholder : Use ? to represent the parameter position and pass the values in order.
• Naming placeholders : Name parameters in the form of :name , suitable for situations where there are many parameters or more complex logic.

For example:

 $stmt = $pdo->prepare("SELECT * FROM users WHERE id = :id AND status = :status");
$stmt->execute(['id' => 1, 'status' => 'active']);

This writing method is not only clear, but also convenient for debugging and reusing.

4. Better error location and debugging support

When using prepared statements, if SQL has syntax problems, an error will usually be reported in the prepare stage, rather than waiting until execution to discover it. This is helpful for quickly positioning problems in the development stage.

In addition, extensions such as PDO or MySQLi support setting error modes, such as throwing exceptions, which facilitate unified handling of errors.

 $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

In general, using prepared statements not only improves application security, but also improves performance and code quality. It should be preferred for any database operation involving user input.

Basically that's it.

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