PHP函数编程实战指南：从基础到高级应用
函数是PHP编程的核心概念之一，也是代码复用和模块化的基础。在我多年的PHP开发经验中，我发现很多初学者对函数的理解还停留在表面。今天我想分享一些关于PHP函数的深入知识和实用技巧。
函数的基本定义和调用
1. 基本语法
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| <?php
function greet($name) {
return "你好，" . $name . "！";
}
echo greet("张三");
function getCurrentTime() {
return date("Y-m-d H:i:s");
}
echo "当前时间：" . getCurrentTime() . "\n";
?>
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2. 函数命名规范
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| <?php
function calculateTotalPrice($price, $tax) {
return $price * (1 + $tax);
}
function validateEmail($email) {
return filter_var($email, FILTER_VALIDATE_EMAIL) !== false;
}
function getUserById($id) {
return ["id" => $id, "name" => "用户" . $id];
}
$price = calculateTotalPrice(100, 0.1);
$isValid = validateEmail("test@example.com");
$user = getUserById(123);
?>
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参数传递详解
1. 值传递（默认方式）
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| <?php
function modifyValue($value) {
$value = $value * 2;
echo "函数内部：$value\n";
}
$number = 10;
modifyValue($number);
echo "函数外部：$number\n";
?>
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2. 引用传递
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| <?php
function modifyByReference(&$value) {
$value = $value * 2;
echo "函数内部：$value\n";
}
$number = 10;
modifyByReference($number);
echo "函数外部：$number\n";
function swap(&$a, &$b) {
$temp = $a;
$a = $b;
$b = $temp;
}
$x = 5;
$y = 10;
echo "交换前：x=$x, y=$y\n";
swap($x, $y);
echo "交换后：x=$x, y=$y\n";
?>
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3. 默认参数
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| <?php
function createUser($name, $age = 18, $city = "北京") {
return [
"name" => $name,
"age" => $age,
"city" => $city
];
}
$user1 = createUser("张三");
$user2 = createUser("李四", 25);
$user3 = createUser("王五", 30, "上海");
print_r($user1);
print_r($user2);
print_r($user3);
?>
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4. 可变参数
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| <?php
function sum(...$numbers) {
$total = 0;
foreach ($numbers as $number) {
$total += $number;
}
return $total;
}
echo sum(1, 2, 3, 4, 5) . "\n";
echo sum(10, 20) . "\n";
function sumTraditional() {
$args = func_get_args();
$total = 0;
foreach ($args as $arg) {
$total += $arg;
}
return $total;
}
echo sumTraditional(1, 2, 3) . "\n";
?>
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5. 类型声明（PHP 7+）
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| <?php
function divide(float $a, float $b): float {
if ($b == 0) {
throw new InvalidArgumentException("除数不能为零");
}
return $a / $b;
}
function processUsers(array $users): int {
return count($users);
}
function findUser(?int $id): ?array {
if ($id === null) {
return null;
}
return $id > 0 ? ["id" => $id, "name" => "用户$id"] : null;
}
try {
echo divide(10.5, 2.5) . "\n";
echo processUsers(["user1", "user2"]) . "\n";
$user = findUser(123);
if ($user) {
echo "找到用户：" . $user["name"] . "\n";
}
} catch (Exception $e) {
echo "错误：" . $e->getMessage() . "\n";
}
?>
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变量作用域和静态变量
1. 局部作用域和全局作用域
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| <?php
$globalVar = "我是全局变量";
function testScope() {
$localVar = "我是局部变量";
global $globalVar;
echo "方法1：$globalVar\n";
echo "方法2：" . $GLOBALS['globalVar'] . "\n";
$GLOBALS['globalVar'] = "全局变量被修改了";
}
testScope();
echo "修改后的全局变量：$globalVar\n";
?>
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2. 静态变量
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| <?php
function counter() {
static $count = 0;
$count++;
echo "调用次数：$count\n";
return $count;
}
counter();
counter();
counter();
function getDatabase() {
static $db = null;
if ($db === null) {
echo "创建数据库连接\n";
$db = new stdClass();
$db->connected = true;
}
return $db;
}
$db1 = getDatabase();
$db2 = getDatabase();
var_dump($db1 === $db2);
?>
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匿名函数和闭包
1. 基本匿名函数
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| <?php
$greet = function($name) {
return "你好，$name！";
};
echo $greet("李四") . "\n";
$numbers = [1, 2, 3, 4, 5];
$squared = array_map(function($n) {
return $n * $n;
}, $numbers);
print_r($squared);
?>
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2. 闭包（使用use关键字）
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| <?php
$message = "外部变量";
$multiplier = 3;
$closure = function($name) use ($message, $multiplier) {
return "$message：$name，乘数是$multiplier";
};
echo $closure("张三") . "\n";
$counter = 0;
$increment = function() use (&$counter) {
$counter++;
echo "计数器：$counter\n";
};
$increment();
$increment();
echo "外部计数器：$counter\n";
?>
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3. 高阶函数应用
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| <?php
function createMultiplier($factor) {
return function($number) use ($factor) {
return $number * $factor;
};
}
$double = createMultiplier(2);
$triple = createMultiplier(3);
echo $double(5) . "\n";
echo $triple(5) . "\n";
function compose($f, $g) {
return function($x) use ($f, $g) {
return $f($g($x));
};
}
$addOne = function($x) { return $x + 1; };
$double = function($x) { return $x * 2; };
$addOneThenDouble = compose($double, $addOne);
echo $addOneThenDouble(5) . "\n";
?>
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递归函数
1. 基本递归
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| <?php
function factorial($n) {
if ($n <= 1) {
return 1;
}
return $n * factorial($n - 1);
}
echo "5的阶乘：" . factorial(5) . "\n";
function fibonacci($n) {
if ($n <= 1) {
return $n;
}
return fibonacci($n - 1) + fibonacci($n - 2);
}
echo "第10个斐波那契数：" . fibonacci(10) . "\n";
?>
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2. 尾递归优化
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| <?php
function factorialNormal($n) {
if ($n <= 1) return 1;
return $n * factorialNormal($n - 1);
}
function factorialTail($n, $acc = 1) {
if ($n <= 1) return $acc;
return factorialTail($n - 1, $n * $acc);
}
echo "普通递归：" . factorialNormal(5) . "\n";
echo "尾递归：" . factorialTail(5) . "\n";
?>
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3. 递归遍历目录
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| <?php
function listDirectory($dir, $level = 0) {
$indent = str_repeat(" ", $level);
if (is_dir($dir)) {
echo $indent . "[目录] " . basename($dir) . "\n";
$files = scandir($dir);
foreach ($files as $file) {
if ($file != "." && $file != "..") {
listDirectory($dir . "/" . $file, $level + 1);
}
}
} else {
echo $indent . "[文件] " . basename($dir) . "\n";
}
}
?>
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错误处理和异常
1. 基本错误处理
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| <?php
function safeDivide($a, $b) {
if ($b == 0) {
trigger_error("除数不能为零", E_USER_ERROR);
return false;
}
return $a / $b;
}
function customErrorHandler($errno, $errstr, $errfile, $errline) {
echo "错误 [$errno]: $errstr 在文件 $errfile 第 $errline 行\n";
}
set_error_handler("customErrorHandler");
$result = safeDivide(10, 0);
?>
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2. 异常处理
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| <?php
class MathException extends Exception {}
function divide($a, $b) {
if ($b == 0) {
throw new MathException("除数不能为零");
}
return $a / $b;
}
function calculateAverage(array $numbers) {
if (empty($numbers)) {
throw new InvalidArgumentException("数组不能为空");
}
$sum = array_sum($numbers);
return $sum / count($numbers);
}
try {
echo divide(10, 2) . "\n";
echo divide(10, 0) . "\n";
} catch (MathException $e) {
echo "数学错误：" . $e->getMessage() . "\n";
} catch (Exception $e) {
echo "其他错误：" . $e->getMessage() . "\n";
} finally {
echo "清理工作\n";
}
try {
$avg = calculateAverage([]);
} catch (InvalidArgumentException $e) {
echo "参数错误：" . $e->getMessage() . "\n";
}
?>
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函数的高级应用
1. 回调函数
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| <?php
function processSuccess($data) {
echo "处理成功：" . json_encode($data) . "\n";
}
function processError($error) {
echo "处理失败：$error\n";
}
function processData($data, $successCallback, $errorCallback) {
if (is_array($data) && !empty($data)) {
$successCallback($data);
} else {
$errorCallback("数据无效");
}
}
processData(["name" => "张三"], "processSuccess", "processError");
processData(null, "processSuccess", "processError");
processData(
["age" => 25],
function($data) { echo "匿名成功回调：" . json_encode($data) . "\n"; },
function($error) { echo "匿名错误回调：$error\n"; }
);
?>
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2. 函数缓存（记忆化）
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| <?php
function memoize($func) {
static $cache = [];
return function() use ($func, &$cache) {
$args = func_get_args();
$key = serialize($args);
if (!isset($cache[$key])) {
$cache[$key] = call_user_func_array($func, $args);
}
return $cache[$key];
};
}
function fibonacciSlow($n) {
if ($n <= 1) return $n;
return fibonacciSlow($n - 1) + fibonacciSlow($n - 2);
}
$fibonacciFast = memoize('fibonacciSlow');
$start = microtime(true);
echo "慢速版本：" . fibonacciSlow(30) . "\n";
echo "耗时：" . (microtime(true) - $start) . "秒\n";
$start = microtime(true);
echo "快速版本：" . $fibonacciFast(30) . "\n";
echo "耗时：" . (microtime(true) - $start) . "秒\n";
?>
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3. 函数装饰器
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| <?php
function timer($func) {
return function() use ($func) {
$start = microtime(true);
$result = call_user_func_array($func, func_get_args());
$end = microtime(true);
echo "函数执行时间：" . ($end - $start) . "秒\n";
return $result;
};
}
function logger($func) {
return function() use ($func) {
$args = func_get_args();
echo "调用函数，参数：" . json_encode($args) . "\n";
$result = call_user_func_array($func, $args);
echo "函数返回：" . json_encode($result) . "\n";
return $result;
};
}
function slowFunction($n) {
sleep(1);
return $n * 2;
}
$timedFunction = timer('slowFunction');
$loggedFunction = logger($timedFunction);
$result = $loggedFunction(5);
?>
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常见错误和最佳实践
1. 避免全局变量污染
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| <?php
$config = ["db_host" => "localhost"];
function getDbHost() {
global $config;
return $config["db_host"];
}
function getDbHostBetter($config) {
return $config["db_host"];
}
class Config {
private static $config = ["db_host" => "localhost"];
public static function get($key) {
return self::$config[$key] ?? null;
}
}
echo Config::get("db_host") . "\n";
?>
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2. 函数单一职责原则
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| <?php
function processUserBad($userData) {
if (empty($userData["name"])) {
throw new Exception("姓名不能为空");
}
return true;
}
function validateUser($userData) {
if (empty($userData["name"])) {
throw new Exception("姓名不能为空");
}
return true;
}
function saveUser($userData) {
return true;
}
function sendWelcomeEmail($userData) {
return true;
}
function logUserCreation($userData) {
return true;
}
function processUserGood($userData) {
validateUser($userData);
saveUser($userData);
sendWelcomeEmail($userData);
logUserCreation($userData);
return true;
}
?>
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3. 合理使用类型声明
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| <?php
class User {
private string $name;
private int $age;
private ?string $email;
public function __construct(string $name, int $age, ?string $email = null) {
$this->name = $name;
$this->age = $age;
$this->email = $email;
}
public function getName(): string {
return $this->name;
}
public function getAge(): int {
return $this->age;
}
public function getEmail(): ?string {
return $this->email;
}
}
function processUsers(array $users): int {
$count = 0;
foreach ($users as $user) {
if ($user instanceof User) {
$count++;
}
}
return $count;
}
?>
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性能优化技巧
1. 避免重复计算
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| <?php
function processItems($items) {
for ($i = 0; $i < count($items); $i++) {
echo $items[$i] . "\n";
}
}
function processItemsBetter($items) {
$count = count($items);
for ($i = 0; $i < $count; $i++) {
echo $items[$i] . "\n";
}
}
function processItemsBest($items) {
foreach ($items as $item) {
echo $item . "\n";
}
}
?>
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2. 合理使用引用传递
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| <?php
function processLargeArray(array &$largeArray) {
foreach ($largeArray as &$item) {
$item = strtoupper($item);
}
unset($item);
}
$data = array_fill(0, 10000, "test");
processLargeArray($data);
?>
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总结
PHP函数编程的核心要点：
- 合理设计函数接口：参数清晰，返回值明确
- 遵循单一职责原则：一个函数只做一件事
- 善用类型声明：提高代码可读性和健壮性
- 理解作用域：合理使用局部、全局和静态变量
- 掌握高级特性：匿名函数、闭包、递归等
- 注重错误处理：使用异常机制处理错误情况
- 考虑性能优化：避免不必要的计算和内存复制
- 保持代码简洁：优先使用内置函数和标准库
通过掌握这些概念和技巧，你可以写出更加优雅、高效的PHP代码。记住，好的函数设计不仅要功能正确，还要易于理解、测试和维护。
希望这篇文章能帮助你更深入地理解PHP函数编程！
