How to write query page using php

In website development, the query page occupies an important position. In this article, we will introduce how to write query pages using PHP.

1. Establishing a database connection

Before we start writing the query page, we need to ensure that the database connection has been established. You can use PHP's mysqli connection function to achieve this:

//建立连接
$conn = new mysqli($dbServername, $dbUsername, $dbPassword, $dbName);

//判断是否成功建立连接
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

2. Get query parameters

In the query page, there are usually some input boxes for entering query conditions. We need to first obtain the query parameters entered by the user and verify their legitimacy. You can use PHP's $_GET or $_POST super global variable to get the parameters:

$searchKeyword = mysqli_real_escape_string($conn, $_POST['search']);

The above mysqli_real_escape_string() function can convert the input Escape the string to avoid SQL injection attacks.

3. Build a SQL statement

After obtaining the query parameters, we can construct a SQL statement for query. SQL statements can be dynamically generated based on different query conditions. For example, a simple SQL query statement can look like this:

$sql = "SELECT * FROM users WHERE name = '".$searchKeyword."'";

Note that we use the $searchKeyword variable in the SQL statement instead of directly splicing the user input into the SQL in the statement. This is also to avoid SQL injection attacks.

4. Execute SQL query

After completing the construction of the SQL statement, we can execute the query. You can use PHP's mysqli_query() function to execute the query:

$result = mysqli_query($conn, $sql);

5. Display query results

Finally, we need to display the query results on the web page. You can use PHP's loop statement to traverse the results of the SQL query and display it in an HTML table:

<table>
    <tr>
        <th>ID</th>
        <th>姓名</th>
        <th>性别</th>
    </tr>
    <?php
    while ($row = mysqli_fetch_array($result)) {
        echo "<tr>";
        echo "<td>".$row['id']."</td>";
        echo "<td>".$row['name']."</td>";
        echo "<td>".$row['gender']."</td>";
        echo "</tr>";
    }
    ?>
</table>

In the above code, we used the mysqli_fetch_array() function to retrieve the results from the query Get the data from the results and output it into an HTML table.

Summary

In this article, we introduced several key steps in using PHP to write query pages: establishing a database connection, obtaining query parameters, constructing SQL statements, executing SQL queries, and displaying search result. With these basic skills, we can easily write powerful query pages and bring more convenient functions to our website.

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