In PHP, both lambda functions and anonymous functions serve similar purposes. They allow us to create functions without giving them a specific name. However, there are some differences between the two.

Lambda functions are defined using the fn keyword, introduced in PHP 7.4:

$lambda = fn($arg1, $arg2) => $arg1 + $arg2;

Anonymous functions are defined using the function keyword:

$anonymous = function($arg1, $arg2) {
    return $arg1 + $arg2;
};

Lambda functions are generally more concise and are often used for simple, one-liner operations.

Anonymous functions offer more flexibility and can have multiple statements and even contain named functions and classes within them.

In a lambda function, variables from the surrounding scope are automatically captured, meaning they can be used inside the lambda without any extra effort.

$x = 10;
$lambda = fn($y) => $x + $y;

In an anonymous function, you need to use the use keyword to import variables from the surrounding scope.

$x = 10;
$anonymous = function($y) use ($x) {
    return $x + $y;
};

Lambda functions can implicitly return the result of the expression without the need for a return statement.

Anonymous functions require a return statement to return a value explicitly.

Lambda functions were introduced in PHP 7.4, so they are only available in PHP 7.4 and later.

Anonymous functions have been available in PHP since version 5.3, making them more widely supported in older PHP versions.

In summary, lambda functions are a more concise and modern way to create simple anonymous functions in PHP, while anonymous functions provide more flexibility and are available in older PHP versions. Your choice between them should depend on your specific use case and the PHP version you are working with.