Why store function as variable in PHP

Question

I've seen this practice in the php docs:

$foo = function() {
    echo 'foo';
}

$foo();

Why would you do that instead of just:

function foo()
{
    echo 'foo';
}

foo();

Answer 1

They're useful in a few ways. Personally I use them because they're easier to control than actual functions.

But also, anonymous functions can do this:

$someVar = "Hello, world!";
$show = function() use ($someVar) {
    echo $someVar;
}
$show();

Anonymous functions can "import" variables from the outside scope. The best part is that it's safe to use in loops (unlike JavaScript) because it takes a copy of the variable to use with the function, unless you specifically tell it to pass by reference with use (&$someVar)

Answer 2

It's also often used to pass callbacks to functions such as array_map and many others