How to use PHP anonymous functions?

Anonymous functions, also known as closure functions, are a function type introduced in PHP 5.3 that allow functions to be defined without names. Its advantages include code simplicity, dynamic creation, and local scope. Common examples of using anonymous functions include using them with array functions such as array_filter() to implement more complex filtering logic, such as filtering arrays based on the even/odd properties of numbers.

How to use PHP anonymous functions

Anonymous functions, also known as closure functions, were introduced in PHP 5.3 A function type that allows functions to be defined without names. This is useful when you need to create functions dynamically or create locally scoped functions within a nested function.

Create anonymous functions

The syntax for creating anonymous functions is very simple:

$anonFunc = function ($args) {
  // 函数主体
};

For example, the following anonymous function calculates the sum of two numbers:

$sum = function ($a, $b) {
  return $a + $b;
};

Calling anonymous functions

Calling anonymous functions is the same as calling ordinary functions:

echo $sum(10, 20); // 输出：30

Advantages of using anonymous functions

• Code simplicity: Anonymous functions can make your code cleaner by eliminating the need to create and name functions.
• Dynamic creation: Anonymous functions can be created dynamically and generate functions with special behavior as needed.
• Local scope: In nested functions, anonymous functions can create local scopes to isolate local variables from the outer scope.

Practical case

Use array_filter() to sort the array

Anonymous functions can be used with array functions ( Such as array_filter()) used together to implement more complex filtering logic. The following example filters an array by the even/odd properties of numbers:

$array = [1, 2, 3, 4, 5, 6, 7, 8];

$even = array_filter($array, function ($num) {
  return $num % 2 == 0;
});

$odd = array_filter($array, function ($num) {
  return $num % 2 != 0;
});

Now, $even will contain all the even numbers in the array, while $odd will contain all the odd numbers.

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