Detailed explanation of the steps to create a PHP query system

PHP (Hypertext Preprocessor) is an open source server-side scripting language that is widely used in the field of web development. PHP can be used to create various applications such as dynamic web pages, e-commerce websites, blogs, and more. In PHP, query is a basic function, and data query can be realized by establishing a query system. The following are the steps to set up a PHP query system.

1. Install PHP

Before you begin, you need to install PHP. If your operating system is Linux or MacOS, you can install it using the following command in the terminal:

sudo apt-get install php

For Windows users, you can download and install PHP from the PHP official website.

2. Create database table

The query system needs to obtain data from a certain data source and query it. Therefore, you need to create a table in the MySQL database to store the data. You can create tables in the database using phpMyAdmin or the command line. The following is an example SQL command to create a table named "query_table":

CREATE TABLE query_table (id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY, name VARCHAR(30) NOT NULL, age INT(3) NOT NULL, gender VARCHAR(10) NOT NULL)

The above command will create a table containing id, name, age and gender. The id is an automatically increased primary key, so there is no need to enter it manually.

3. Connect to MySQL database

The PHP query system needs to connect to the MySQL database to obtain data from it. You can use the following code to connect to the MySQL database:

$servername = "localhost";
$username = "yourusername";
$password = "yourpassword";
$dbname = "yourdatabase";

$conn = new mysqli($servername, $username, $password, $dbname);

if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

In the above code, $servername is the name of the MySQL server, $username and $password are the username and password required to connect to MySQL, $dbname is The name of the database to connect to. If the connection fails, an error message is printed.

4. Create query form

To implement a query system, you need to create a form on a Web page to receive queries entered by users. The form should contain some input fields and a submit button. Here is an example of a simple query form:

<form method="POST" action="query.php">
    <label for="last_name">Last Name: </label>
    <input type="text" name="last_name" id="last_name">
    <label for="first_name">First Name: </label>
    <input type="text" name="first_name" id="first_name">
    <input type="submit" value="Search">
</form>

This form contains two input fields (last name and first name) and a submit button. When the form is submitted, a PHP script named "query.php" is called to handle the query.

5. Handling the query

Please make sure to include the code to connect to the MySQL database in the query script. Before processing a query, you need to validate user-entered data and ensure that the data is query-ready. Here is the simple validation and query processing code:

$last_name = $_POST["last_name"];
$first_name = $_POST["first_name"];

if (!empty($last_name) || !empty($first_name)) {
    $sql = "SELECT * FROM query_table WHERE name LIKE '%$last_name%' AND name LIKE '%$first_name%'";
    $result = $conn->query($sql);

    if ($result->num_rows > 0) {
        echo "<table><tr><th>ID</th><th>Name</th><th>Age</th><th>Gender</th></tr>";
        while ($row = $result->fetch_assoc()) {
            echo "<tr><td>" . $row["id"] . "</td><td>" . $row["name"] . "</td><td>" . $row["age"] . "</td><td>" . $row["gender"] . "</td></tr>";
        }
        echo "</table>";
    } else {
        echo "No results found.";
    }
} else {
    echo "Please enter at least one search criteria.";
}

In the above code, we first get the name entered by the user from the POST request. We then ensure that the input fields all have values ​​and then use the LIKE operator to search for the corresponding records in the query table. If there are records, use a while loop to display them all on the web page. Otherwise, a "No results found" message is output. If the input field has no value, a prompt message is output.

6. Improve query system

To improve the query system, you can add more query methods, such as filtering by age or gender. You can also use AJAX technology to make queries more dynamic and display results without refreshing the page.

In short, through the steps provided in this article, you can quickly create a basic PHP query system and make it more dynamic, flexible and powerful through improvements.

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