匿名函數(shù)是無名稱的函數(shù)，常作為回調(diào)或值傳遞；閉包是能捕獲外部變量的匿名函數(shù)。 1. 匿名函數(shù)用於array_map等回調(diào)場(chǎng)景，使代碼簡(jiǎn)潔；2. 閉包通過use引入外部變量，實(shí)現(xiàn)對(duì)外部作用域變量的訪問；3. 適用於事件處理、延遲執(zhí)行、短期邏輯等場(chǎng)景，提升代碼可讀性但需注意調(diào)試和維護(hù)複雜度。

Anonymous functions and closures in PHP might sound a bit technical at first, but they're actually pretty useful once you get the hang of them. In short, an anonymous function is a function without a name — it's often used as a callback or passed around as a value. A closure is a type of anonymous function that can also capture variables from its surrounding scope.

What's an anonymous function?

An anonymous function is just like a regular function, except it doesn't have a name. You define it inline, usually to pass it somewhere else — like using it as a callback for array functions or event handlers.

Here's a basic example:

 $numbers = [1, 2, 3, 4];
$squared = array_map(function($n) {
    return $n * $n;
}, $numbers);

In this case, we're passing an anonymous function directly into array_map instead of defining a separate named function. It keeps things clean when the logic is simple and only needed once.

You'll see these most often in places where a function expects a callable — things like array_filter , usort , or Laravel routes and middleware.

What makes a closure different?

A closure is basically an anonymous function that "closes over" variables from the parent scope. That means it can access variables that are defined outside of its own body — something regular anonymous functions can't do by default.

Here's how that looks:

 $factor = 2;
$double = function($n) use ($factor) {
    return $n * $factor;
};

echo $double(5); // Outputs: 10

The key part here is the use ($factor) — that's how PHP lets the closure bring in external variables. Without use , the function wouldn't know about $factor .

This is super handy when you need to inject some context into a function without passing it every time you call it.

When should you use them?

There are a few common scenarios where closures and anonymous functions really shine:

• Callbacks – Especially with array functions ( array_map , array_filter , etc.)
• Event handling – In frameworks like Laravel, where you attach logic to events on the fly.
• Delayed execution – Storing logic in a variable to run later, maybe conditionally.
• Short-lived logic – For small bits of code that don't need to be reused elsewhere.

They help keep your code concise and focused, especially when the alternative would be writing a bunch of one-off helper functions.

It's worth noting that while closures are powerful, they can sometimes make debugging trickier if you're not careful with variable scope. Also, overusing them for complex logic can hurt readability.

So yes, they're flexible — but like any tool, best used where appropriate.

基本上就這些。

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