How to use PHP PDO extension to connect to MySQL database

In PHP applications, operations that require modification of the database are one of the common requirements. PHP Data Object (PDO) provides a safe and efficient way to operate on relational databases.

This article will introduce how to use PDO extension to connect to MySQL database, and demonstrate through examples how to use PDO to modify database data.

Connecting to MySQL database

Before using PDO, you first need to connect to the database. The following is a sample code for connecting to a MySQL database:

//数据库连接参数
$host = 'localhost';
$dbname = 'test';
$username = 'root';
$password = '';

//连接数据库
try {
    $db = new PDO("mysql:host=$host;dbname=$dbname", $username, $password);
} catch(PDOException $e) {
    echo $e->getMessage();
}

In the above code, we connect to the database through the constructor of the PDO class. First, specify the host name and database name of the MySQL database, and then pass in the user name and password to connect.

Modify database data

After the connection is successful, let’s look at how to use PDO to modify database data. We assume there is a student table containing id, name and age fields. Next, we will demonstrate how to use PDO to modify data on this table.

1. Update a single field

We can use PDO's prepare() function to perform modification operations. The following is a code example for updating the record with id 1 in the student table:

//更新数据
$id = 1;
$newName = 'Tom';
$sql = "UPDATE student SET name=:name WHERE id=:id";
$stmt = $db->prepare($sql);
$stmt->bindParam(':id', $id, PDO::PARAM_INT);
$stmt->bindParam(':name', $newName, PDO::PARAM_STR);
$stmt->execute();

In the above code, we first define the id and new name value of the record to be updated. We then update name to $newName via the UPDATE statement, where :id and :name are placeholders. Next, we use PDO's prepare() function to prepare the SQL statement and bind the values ​​​​of $id and $newName through the bindParam() function. Finally, we call the execute() function to perform the update operation.

2. Update multiple fields

If you want to update multiple fields, we can use a method similar to the above. The following is a code example that updates the name and age fields of the record with id 1 in the student table:

//更新数据
$id = 1;
$newName = 'Tom';
$newAge = 20;
$sql = "UPDATE student SET name=:name, age=:age WHERE id=:id";
$stmt = $db->prepare($sql);
$stmt->bindParam(':id', $id, PDO::PARAM_INT);
$stmt->bindParam(':name', $newName, PDO::PARAM_STR);
$stmt->bindParam(':age', $newAge, PDO::PARAM_INT);
$stmt->execute();

In the above code, we update name and age to new values ​​through the UPDATE statement. Note that we need to bind corresponding parameters for each field to be updated.

3. Batch update records

If we want to update data in batches, we can use the transaction function of PDO. The following is a code example for updating multiple student records:

//更新多条数据
$students = array(
    array('id'=>1, 'name'=>'Tom', 'age'=>20),
    array('id'=>2, 'name'=>'Jack', 'age'=>22),
    array('id'=>3, 'name'=>'Lily', 'age'=>21)
);

try {
    $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $db->beginTransaction();
    $sql = "UPDATE student SET name=:name, age=:age WHERE id=:id";
    $stmt = $db->prepare($sql);
    foreach ($students as $student) {
        $stmt->bindParam(':id', $student['id'], PDO::PARAM_INT);
        $stmt->bindParam(':name', $student['name'], PDO::PARAM_STR);
        $stmt->bindParam(':age', $student['age'], PDO::PARAM_INT);
        $stmt->execute();
    }
    $db->commit();
} catch (PDOException $e) {
    $db->rollback();
    echo $e->getMessage();
}

In the above code, we define an array $students that contains the records to be updated. Then, we implemented the transaction operation by using the beginTransaction() function and the commit() function. In the loop, we bind the id, name and age parameters of each record and execute the SQL statements respectively.

Summary

Using PDO to modify database data is a safe and reliable method. In this article, we explain how to use PDO to connect to the MySQL database, and demonstrate through examples how to use PDO to modify database data. It is worth mentioning that we also introduced how to use the transaction function of PDO to update records in batches, which is a very practical skill.

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