PHP常用代码样例，这些示例是否涵盖了所有基础需求？

PHP常用代码样例

以下是一些常用的PHP代码样例，涵盖了基本的语法和功能。

1. 输出文本

<?php
echo "Hello, World!";
?>

2. 变量声明和使用

<?php
$name = "Alice";
echo "Hello, $name!";
?>

3. 条件语句

<?php
$age = 25;
if ($age >= 18) {
    echo "You are an adult.";
} else {
    echo "You are a minor.";
}
?>

4. 循环语句

4.1 for循环

<?php
for ($i = 0; $i < 5; $i++) {
    echo $i . "<br>";
}
?>

4.2 while循环

<?php
$count = 0;
while ($count < 5) {
    echo $count . "<br>";
    $count++;
}
?>

5. 数组操作

<?php
$fruits = array("apple", "banana", "cherry");
echo $fruits[0]; // 输出 "apple"
?>

6. 函数定义与调用

<?php
function greet($name) {
    echo "Hello, $name!";
}
greet("Bob"); // 输出 "Hello, Bob!"
?>

7. 表单处理

<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $name = $_POST["name"];
    echo "Hello, $name!";
}
?>
<form method="post">
    Name: <input type="text" name="name"><br>
    <input type="submit">
</form>

8. 数据库连接与查询

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";
// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);
// 检查连接
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}
// 执行SQL查询
$sql = "SELECT id, firstname, lastname FROM MyGuests";
$result = $conn->query($sql);
if ($result->num_rows > 0) {
    // 输出数据
    while($row = $result->fetch_assoc()) {
        echo "id: " . $row["id"]. " Name: " . $row["firstname"]. " " . $row["lastname"]. "<br>";
    }
} else {
    echo "0 results";
}
$conn->close();
?>