Summary of PHP Anonymous Functions

What are Anonymous Functions?

• Definition: Anonymous functions, also known as closures, are functions that do not have a name.
• Usage: They are commonly used as arguments for other functions or to encapsulate functionality within a block of code.

Key Concepts

Syntax

• An anonymous function is defined using the function keyword followed by a set of parentheses and curly braces.

  $functionName = function($parameters) {
      // Code to execute
  };

Usage as Callbacks

• Anonymous functions can be used as callbacks in functions like array_map(), array_filter(), etc.

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

Capturing Variables

• They can capture variables from the surrounding scope using the use keyword.

$a = 10;
$b = 20;

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

echo $sum(); // Outputs 30

Benefits of Using Anonymous Functions

• Simplicity: They make your code cleaner and easier to read.
• Encapsulation: They allow you to limit the scope of your functions and avoid polluting the global namespace.

Example

Here’s a complete example that demonstrates the use of an anonymous function to filter an array:

$numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
$evenNumbers = array_filter($numbers, function($num) {
    return $num % 2 === 0;
});

print_r($evenNumbers); // Outputs: [2, 4, 6, 8, 10]

Conclusion

• Anonymous functions in PHP provide a powerful way to create functions on the fly, enhancing the flexibility and readability of your code.
• They are particularly useful when working with higher-order functions, where functions are passed as parameters.