Dynamic Websites Made Easy: Learning the Basics of PHP

PHP is a general-purpose scripting language specifically designed for web development to create websites that dynamically respond to user input. Its basic syntax includes PHP tags, echo statements, variables (declared with the $ symbol), data types (int, float, etc.), conditional statements (such as if statements), loops (for and while loops), and the ability to connect to a database (such as MySQL). A simple message board practical case demonstrates the practical application of using PHP for data processing and page interaction.

Introduction to Dynamic Website Development: PHP Basics

PHP (Hypertext Preprocessor) is a general-purpose scripting language designed specifically for web development. By using PHP we can create dynamic websites that respond to user input.

Basic syntax of PHP

A simple PHP script looks like this:

<?php

  // 这是 PHP 代码
  echo "你好，世界！";

?>

• The PHP code is contained within the <?php and ?> tags . The
• echo statement outputs the string "Hello, world!" to a web browser.

Variables

Variables are used to store data. They can be declared with the $ symbol:

$name = "John Doe";

Now, we can use the variable $name to access its value.

Data types

PHP supports a variety of data types, including:

int (整数)
float (小数)
string (字符串)
boolean (布尔值)
array (数组)

Conditional statements

Conditional statements are used to control the execution of code. The most common conditional statement is the if statement:

if ($age >= 18) {
  echo "成年";
} else {
  echo "未成年";
}

Loop

Loop is used to repeatedly execute a block of code. There are two main types of loops:

• for Loop: Used to execute a loop a known number of times.
• while Loop: used to execute loops whose conditions are true.

Database Connections

PHP can connect to databases such as MySQL, PostgreSQL, and SQL Server. This allows us to read and write data from the database.

// 连接到 MySQL 数据库
$conn = mysqli_connect("localhost", "root", "password", "test");

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

// 获取结果并显示
while ($row = mysqli_fetch_array($result)) {
  echo $row["name"];
}

Practical case: a simple message board

We create a simple message board that allows users to enter and view messages.

<!-- index.html -->
<form action="save.php" method="POST">
  <input type="text" name="message">
  <input type="submit" value="发表">
</form>

<!-- save.php -->
<?php

// 获取表单数据
$message = $_POST["message"];

// 连接到数据库
$conn = mysqli_connect("localhost", "root", "password", "test");

// 插入留言
$query = "INSERT INTO messages (message) VALUES ('$message')";
mysqli_query($conn, $query);

// 重定向到列表页面
header("Location: list.php");

?>

<!-- list.php -->
<?php

// 连接到数据库
$conn = mysqli_connect("localhost", "root", "password", "test");

// 获取留言
$query = "SELECT * FROM messages";
$result = mysqli_query($conn, $query);

// 显示留言
while ($row = mysqli_fetch_array($result)) {
  echo $row["message"];
  echo "<br>";
}

?>

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