How to query all information in the database in php

PHP is a very popular programming language, which is widely used in dynamic web development and database query. This article will introduce how to use PHP to query all the information in the database. I hope it will be helpful to readers in need.

First, we need to prepare some environments, including a Web server, a database and some sample data. We can use XAMPP as our development environment, which includes Apache server, MySQL database and PHP interpreter. After installing XAMPP, we need to create a database table for testing. You can use the following SQL statement:

CREATE TABLE `test_table` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  `age` int(11) NOT NULL,
  `gender` varchar(10) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

This SQL statement creates a table named test_table, including id, name, age and gender four columns. Among them, the id column is an auto-incrementing column, used to identify each row of data. We can insert some test data into this table, for example:

INSERT INTO `test_table` (`name`, `age`, `gender`) VALUES 
('张三', 20, '男'),
('李四', 22, '女'),
('王五', 25, '男'),
('赵六', 30, '女');

Now that we have prepared the data for testing, let's start writing PHP code to query all the information in this database table.

First, we need to establish a connection with the database. In PHP, we can use the mysqli extension to operate the MySQL database. The specific code is as follows:

$servername = "localhost";
$username = "root";
$password = "";
$dbname = "test_database";

// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);

// 检查连接是否成功
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

In this example, the MySQL database we connect to is the local test_database, and the username and password are default values. If the connection fails, the program will print an error message and terminate.

Next, we need to write SQL statements to query the information in the database. In this example, we need to query all the information in the test_table table, that is, SELECT * FROM test_table. We can use the mysqli_query function to execute this SQL statement. The specific code is as follows:

$sql = "SELECT * FROM test_table";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
    // 输出数据
    while($row = mysqli_fetch_assoc($result)) {
        echo "id: " . $row["id"]. " - Name: " . $row["name"]. " - Age: " . $row["age"]. " - Gender: " . $row["gender"]. "<br>";
    }
} else {
    echo "0 结果";
}

In this code snippet, we use the mysqli_fetch_assoc function to obtain the query results row by row and output the id, name, age and gender. If the query result is empty, the program will output a "0 results" message.

The above is the basic process of using PHP to query all the information in the database. The complete code is as follows:

connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 执行SQL查询
$sql = "SELECT * FROM test_table";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
    // 输出数据
    while($row = mysqli_fetch_assoc($result)) {
        echo "id: " . $row["id"]. " - Name: " . $row["name"]. " - Age: " . $row["age"]. " - Gender: " . $row["gender"]. "<br>";
    }
} else {
    echo "0 结果";
}

// 关闭连接
mysqli_close($conn);
?>

To sum up, this article introduces how to use PHP to query all the information in the database. Readers can make corresponding modifications and extensions according to their own needs. At the same time, we should also pay attention to issues such as data security and performance optimization to avoid potential security risks and efficiency issues.

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