Closure in JavaScript vs PHP — What’s the Difference?

✅ What is a Closure (in both)?

A closure is a function that captures variables from its surrounding scope and can use them even after the outer function has finished.

But the syntax and behavior differ between JavaScript and PHP.

📘 JavaScript Closures

✅ Syntax Example:

function outer() {
  let count = 0;
  return function inner() {
    count++;
    console.log(count);
  };
}

const counter = outer();
counter(); // 1
counter(); // 2

✅ inner() remembers count, even after outer() has returned — this is a closure.

🔹 JS Closures:

• Created when an inner function uses variables from the outer scope.
• Supports lexical scoping.
• Widely used in async callbacks, event handling, functional programming, etc.
• Captured variables are still live in memory.

🐘 PHP Closures

✅ Syntax Example:

function outer() {
  $count = 0;
  return function () use (&$count) {
    $count++;
    echo $count . PHP_EOL;
  };
}

$counter = outer();
$counter(); // 1
$counter(); // 2

✅ In PHP, closures must explicitly import variables using the use keyword.

🔹 PHP Closures:

• Created with function() use ($var) syntax.
• Variables are not automatically captured — you must declare them.
• Can pass by value or by reference (&).
• Often used in array functions (array_map, array_filter), dependency injection, or functional-style code.

⚖️ Key Differences: JS vs PHP Closure

📝 Summary (Easy to Remember)

💬 Final Thoughts

In JavaScript, closures are natural and automatic.
In PHP, closures are explicit and controlled, using use() to bring in variables.

Both are useful, just different in style and usage.