A simple guide to the underlying development principles of PHP: database connection and query

A simple guide to PHP underlying development principles: database connection and query

Overview:
In modern web development, the database is an indispensable part. As a widely used server-side language, PHP provides many easy ways to connect and query databases. However, understanding the underlying development principles of PHP can help us better understand and optimize the process of database connection and query. This article will briefly introduce the principles of database connection and query in PHP underlying development, and give some examples.

Database connection:
In PHP, the most commonly used database operation extensions are MySQLi and PDO. Regardless of which extension you use, the process of connecting to the database is similar. First, we need to establish a connection to the database by calling the functions provided by the relevant extension. Next, we can execute SQL statements to operate the database.

The sample code is as follows, using the PDO extension to connect to the MySQL database:

$host = "localhost";
$dbname = "database_name";
$username = "username";
$password = "password";

try {
    $pdo = new PDO("mysql:host=$host;dbname=$dbname", $username, $password);
    echo "成功连接到数据库";
} catch (PDOException $e) {
    echo "连接失败：" . $e->getMessage();
}

In this code, we create a through new PDO() PDO object and pass in the connection parameters of the database. If the connection is successful, "Successfully connected to the database" will be output. If the connection fails, a PDOException will be thrown and an error message will be output.

Execute query:
Once we connect to the database, we can then execute the query operation. In the underlying development of PHP, we can use the query() function to execute SQL query statements.

The sample code is as follows, using PDO extension to query all records from the table "users":

$statement = $pdo->query("SELECT * FROM users");
while ($row = $statement->fetch()) {
    echo $row['name'] . "<br>";
}

In this code, we use the query() function to execute A "SELECT" statement was issued to query all records in the table "users". Then, we use the fetch() function to get the query results row by row. Each row of data is returned as an associative array, and we can access the value of each field by index. In this example, we print out the value of the "name" field for each row.

Summary:
By learning the principles of database connection and query in PHP underlying development, we can better understand and optimize database operations. The process of connecting to the database mainly includes two steps: establishing a connection and executing a query. By calling the functions provided by relevant extensions, we can easily connect to the database and execute various SQL query statements.

However, this is just the tip of the iceberg of database operations in PHP underlying development. If you have a deeper interest in PHP's underlying development, I encourage you to explore more database operation functions and underlying principles. Only through continuous learning and practice can we become more proficient and professional in PHP underlying development.

Reference materials:

• PHP manual: https://www.php.net/manual/en/
• PHP MySQLi extension: https://www .php.net/manual/en/book.mysqli.php
• PHP PDO extension: https://www.php.net/manual/en/book.pdo.php

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