How does php mysqli return query results in the form of an associative array?

When using PHP to interact with MySQL for data, we often need to perform database query operations. After executing the query operation, we need an effective way to return the query results to the user. In MySQL query results, data is usually returned in the form of tables. In PHP, you can use associative arrays to return query results to a more friendly data format, which is convenient for us to display and process.

1. What is an associative array

Simply put, an array (Array) is a data type that can save multiple data, and each data can be retrieved through a specified index. access. Associative Array is a special type of array that stores data in the form of "key" and "value". Different from ordinary arrays, the index of an associative array is no longer a number, but a string or number specified by ourselves.

In PHP, we can use an associative array to represent it as follows:

$array = array(
    "姓名" => "张三",
    "年龄" => 20,
    "性别" => "男",
);

Each element in this array consists of a "key" and a "value" , we can use the key value of the array to access the corresponding value. For example, we can use $array["name"] to access the name elements in the array.

2. Use mysqli query results to return associative arrays

Below we will learn how to use mysqli to query the database and return the query results in the form of associative arrays.

1. Connecting to the database

Before using mysqli to perform query operations, we need to establish a database connection first. You can use the following code:

// 建立数据库连接
$mysqli = new mysqli("localhost", "username", "password", "database_name");

where "localhost" represents the server address where the MySQL database is located, "username" and "password" respectively Represents the user name and password, "database_name" is the name of the database to be connected.

2. Perform query operations

After connecting to the MySQL database, we need to perform query operations to obtain the data we need. In mysqli, you can use the following code to perform database query operations:

// 执行查询操作
$result = $mysqli->query("SELECT * FROM table_name");

where"SELECT * FROM table_name" is the SQL query statement we need to execute, $result It is the return value of the query result. * here means selecting all data.

3. Processing query results

We can return the mysqli query results as an associative array to facilitate our data operation and display.

// 处理查询结果
$rows = array();
while ($row = $result->fetch_assoc()) {
    $rows[] = $row;
}

In this code, we get one row of data from $result at a time and convert it into an associative array $row. After each loop, $row is added to a $rows array. Finally, $rows holds an associative array of all query results.

4. Close the database connection

After all database operations are completed, we need to close the database connection:

// 关闭数据库连接
$mysqli->close();

3. Summary

Through associative arrays, we can process and display mysqli query results more conveniently. Use mysqli's fetch_assoc() function to convert the query results into an associative array at one time for subsequent use. At the same time, when using mysqli for database operations, we also need to pay attention to some security issues and prevent attacks such as SQL injection as much as possible. Finally, we can use the exception handling mechanism to handle possible exceptions to make the code more robust and reliable.

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