Focus on PHP PDO query string

PHP and MySQL are two very popular systems in the well-known technology field. PHP provides a traditional page programming language, while MySQL provides powerful database operation capabilities, so they are usually used together to create dynamic websites.

However, querying data is a very critical task when using PHP with MySQL. In this article, we will focus on PHP PDO query string, which is a PHP extension library for querying databases.

What is PHP PDO?

PDO (PHP Data Objects) is a PHP extension library that provides a common interface for interacting with databases. It can be used to connect to many different types of databases, such as MySQL, PostgreSQL, and Oracle.

PDO provides an object-oriented API that supports transactions, prepared statements, connection pools and other functions, so using it can make the code more stable and reusable.

Using PDO for query

How to use PDO for query?

First, we need to connect to the database using PDO:

$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    // 设置 PDO 错误模式为异常
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    echo "Connected successfully";
} catch(PDOException $e) {
    echo "Connection failed: " . $e->getMessage();
}

Now, we have successfully connected to the database. The next step is to query the data. We can use PDO's query() method to execute the query:

$sql = "SELECT * FROM users";
$result = $conn->query($sql);

This will return a PDOStatement object, on which we can call fetch() or fetchAll() to get the query result data:

while($row = $result->fetch()) {
    echo $row["name"] . "<br>";
}

We can also use prepared statements to perform safer queries. Prepared statements allow us to use placeholders to replace variables in the query, thereby avoiding SQL injection attacks:

$stmt = $conn->prepare("SELECT * FROM users WHERE name = :name");
$stmt->bindParam(':name', $name);
$name = "John";
$stmt->execute();

In this case, PDO will automatically match the variable value with the placeholder and execute the query .

Summary

In PHP, it is very convenient to use PDO for query. It provides a safe, reliable and efficient database access method, allowing developers to operate the database more easily. By studying this article, you have mastered how to use PDO for query. Hope this helps.

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