How to implement simple query operation in php?

In web development, data storage and management are a very important part. As a commonly used server-side scripting language, PHP can implement various operations very conveniently.

This article will focus on explaining how to use PHP to implement simple query operations to help beginners get started quickly.

1. Connect to the database

First, we need to connect to the database using PHP. Normally, we will use MySQL database.

Open the PHP code and connect to the MySQL database through the following code:

<?php
$servername = "localhost";
$username = "username";
$password = "password";

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

// 检测连接是否成功
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}
echo "连接成功";
?>

This code will connect to the MySQL database on the local host and output "Connection successful". If the connection fails, "Connection failed" and an error message will be output.

2. Query data

When the database connection is successful, we can start querying the data.

We use the SELECT statement to query data. The basic syntax of the query statement is as follows:

SELECT column1, column2, ... FROM table_name

Among them, column1, column2, etc. represent the column names to be queried, and table_name represents the table name to be queried.

For example, if we want to query all the data in the "users" table, we can use the following code:

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

In this code, $sql is the query statement to be executed, and $result is the query result.

3. Processing query results

The query result is usually a result set, that is, a table containing multiple rows of data. We need to use PHP to iterate through the result set to get each row of data.

For example, if we want to print out the names and emails of all records in the "users" table, we can use the following code:

if ($result->num_rows > 0) {
    // 遍历数据
    while($row = $result->fetch_assoc()) {
        echo "姓名: " . $row["name"]. " - 邮箱：" . $row["email"];
    }
} else {
    echo "0 结果";
}

In the code, we use the fetch_assoc() function to get each A row of data. This function returns an associative array where each key represents a column name and each value represents a column value.

4. Close the database connection

After completing the query operation, we need to close the database connection and release resources.

Use the following code to close the database connection:

$conn->close();

The above is the basic process for implementing simple query operations in PHP. Of course, in practical applications, we also need to consider issues such as data security and query efficiency.

To sum up, through the introduction of this article, we can initially master the basic skills of PHP query operation, and hope it will be helpful to readers.

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