How to query the database and output a two-dimensional array in PHP

PHP is the most commonly used Web development language, and database query is also one of its most used functions. During the development process, it is a common operation to use PHP to query the database and output the results as a two-dimensional array.

So, before starting this article, let’s first introduce what a two-dimensional array is. In PHP, an array can be thought of as an ordered collection of data, while a two-dimensional array is an array containing another array. Usually, we use two-dimensional arrays to store and process tabular data or multi-dimensional data, etc.

Now, let us explore how to use PHP to query the database and output a two-dimensional array.

1. Connect to the database

Before using PHP to query the database, you first need to connect to the database. We can use PHP's built-in function mysqli_connect() to connect to the MySQL database. When connecting, you need to provide information such as the host address of the database, user name, password, and the name of the database to be connected.

The following code shows how to connect to the database:

$db_host = "localhost"; // 主机地址
$db_user = "root";      // 用户名
$db_pass = "password";  // 密码
$db_name = "example";   // 要连接的数据库名称

// 创建连接
$conn = mysqli_connect($db_host, $db_user, $db_pass, $db_name);

// 检查连接是否成功
if (!$conn) {
    die("连接失败： " . mysqli_connect_error());
}
echo "连接成功！";

In this example, we use the mysqli_connect() function to connect to the database. If the connection fails, the connection failure message will be output.

2. Query the database

After connecting to the database, you can perform database queries. We can use the mysqli_query() function to execute the query statement and store the results in a variable. In this example, we query all rows in the database table and store the results in the variable $result.

$sql = "SELECT * FROM users"; // 查询语句
$result = mysqli_query($conn, $sql); // 执行查询语句

In this example, the $sql variable stores the query statement, and the mysqli_query() function executes the statement and stores the result in the $result variable.

3. Output a two-dimensional array

The query results are usually returned in the form of a one-dimensional array, but we can use the mysqli_fetch_all() function to convert the query results into a two-dimensional array. The following code shows how to convert the query results into a two-dimensional array:

$rows = mysqli_fetch_all($result, MYSQLI_ASSOC);
print_r($rows); // 输出二维数组

In this example, use the mysqli_fetch_all() function to convert the results into a two-dimensional array. The first parameter is the query result, and the second parameter is the query result. The parameter MYSQLI_ASSOC refers to converting the query results into an associative array. After the conversion is completed, use the print_r() function to output the array.

Finally, let’s take a look at the complete code:

$db_host = "localhost"; // 主机地址
$db_user = "root";      // 用户名
$db_pass = "password";  // 密码
$db_name = "example";   // 要连接的数据库名称

// 创建连接
$conn = mysqli_connect($db_host, $db_user, $db_pass, $db_name);

// 检查连接是否成功
if (!$conn) {
    die("连接失败： " . mysqli_connect_error());
}
echo "连接成功！";

// 查询数据表
$sql = "SELECT * FROM users"; // 查询语句
$result = mysqli_query($conn, $sql); // 执行查询语句

// 把结果转换成二维数组
$rows = mysqli_fetch_all($result, MYSQLI_ASSOC);

// 输出二维数组
print_r($rows);

// 关闭连接
mysqli_close($conn);

In the above code, in addition to the operations of connecting to the database, querying the data table and outputting the two-dimensional array, we also used mysqli_close at the end () function to close the database connection.

Summary

When using PHP to query the database, outputting the query results as a two-dimensional array is a very common operation. Through the introduction of this article, you learned how to connect to the database, query the data table, and output the query results as a two-dimensional array. If you want to learn more about PHP database query operations in more detail, you can also read PHP official documentation or other related tutorials.

The above is the detailed content of How to query the database and output a two-dimensional array in PHP. For more information, please follow other related articles on the PHP Chinese website!