API¶

The api documentation is broken up into 2 parts: Middleware documentation and Middleware Stack documentation.

Middleware Functions¶

Closure compose(array $mws, callable $last = null, callable $invoke = null)

Composes a set of middleware into a handler.

<?php

$handler = mw\compose([
    function($a, $b, $next) {
        return $a . $b;
    },
    function($a, $b, $next) {
        return $next($a . 'b', $b . 'd');
    }
]);

$res = $handler('a', 'c');
assert($res === 'abcd');

The middleware stack passed in is executed in LIFO order. So the last middleware will be executed first, and the first middleware will be executed last.

After composing the stack of middleware, the resulting handler will share the same signature as the middleware except that it won’t have the $next.

The final parameter is a callable with the same interface as call_user_func (function($function_name, ...$params)) and that is the defaulted value if no $invoke is set. The $invoke function is used to actually invoke or call the middleware. This allows for neat things like container aware middleware where a middleware is just a reference to an entry in a service container. See Advanced Usage for more detail.

Formally, the middleware signature is exactly the same as the resulting composed handler except that they have 2 additional parameters: $next and $invoke.

Handler Signature:

function(...$params): mixed

Middleware Signature:

function(...$params, $next, $invoke): mixed

Closure group(array $mws)

Creates a new middleware composed as one from a middleware stack.

Internally, this calls the compose function, so the same behaviors will apply to this function.

<?php

/** some middleware that will append values to the parameter */
function appendMw($c) {
    return function($s, $next) use ($c) {
        return $next($s . $c);
    };
}

$handler = mw\compose([
    function($s) { return $s; },
    append('d'),
    mw\group([
        append('c'),
        append('b'),
    ]),
    append('a'),
]);

$res = $handler('');
assert($res === 'abcd');

On the surface, this doesn’t seemv very useful, but the ability group middleware into one allows you to then apply other middleware onto a group.

For example, you can do something like:

$grouped = mw\group([
    // ...
]);
mw\filter($grouped, $predicate);

In this example, we just filted an entire group of middleware

Closure lazy(callable $mw_gen)

Lazily creates and executes middleware when it’s executed. Useful if the middleware needs to be generated from a container or if it has expensive dependencies that you only want initialized if the middleware is going to be executed.

<?php

$mw = lazy(function() {
    return expensiveMw($expensive_service_that_was_just_created);
});

The expensive service won’t be created until the $mw is actually executed

Closure filter(callable $mw, callable $predicate)

Either applies the middleware or skips it depending on the result of the predicate. This if very useful for building conditional middleware.

<?php

$mw = function() { return 2; };
$handler = mw\compose([
    function() { return 1; },
    mw\filter($mw, function($v) {
        return $v == 4;
    })
]);
assert($handler(5) == 1 && $handler(4) == 2);

In this example, the stack of middleware always returns 1, however, the filtered middleware gets executed if the value is 4, and in that case, it returns 2 instead.

Invoke Functions¶

Closure pimpleAwareInvoke(Pimple\Container $c, $invoke = ‘call_user_func’): invokes middleware while checking if the mw is a service defined in the pimple container

Stack Functions¶

MwStack stack($name, array $entries = [], $invoke = null)

Creates a MwStack instance. Every stack must have a name which is just a personal identifier for the stack. It’s primary use is for errors/exceptions that help the user track down which stack has an issue.

<?php

$stack = mw\stack('demo stack');
$stack->push($mw)
    ->unshift($mw1);

// compose into handler
$handler = $stack->compose();
// or, use as a grouped middleware
$handler = mw\compose([
    $mw2,
    $stack
]);

array stackEntry(callable $mw, $sort = 0, $name = null)

Creates an entry for the MwStack. This is only used if you want to initialize a stack with entries, else, you’ll just be using the stack methods to create stack entries.

<?php

$stack = mw\stack('demo stack', [
    stackEntry($mw1, 0, 'mw1'),
    stackEntry($mw2),
    stackEntry($mw3, 5, 'mw3'),
]);
// equivalent to
$stack = mw\stack('demo stack')
    ->push($mw1, 0, 'mw1')
    ->push($mw2)
    ->push($mw3, 5, 'mw3');

MwStack stackMerge(...$stacks)

Merges stacks into one another. The resulting stack has the same name as the first stack in the set. The values from the later stacks will override the values from the earlier stacks.

<?php

$a = mw\stack('stack', [
    mw\stackEntry($mw1),
    mw\stackEntry($mw2),
    mw\stackEntry($mw3, 0, 'mw')
]);
$b = mw\stack('stack', [
    mw\stackEntry($mw4, 0, 'mw'),
]);
$c = mw\stackMerge($a, $b);
// stack $c is equivalent to
$c = mw\stack('stack')
    ->push($mw1)
    ->push($mw2)
    ->push($mw4, 0, 'mw')

class MwStack implements Countable¶

The stack presents a mutable interface into a stack of middleware. Middleware can be added with a name and priority. Only one middleware with a given name may exist. Middleware that are last in the stack will be executed first once the stack is composed.

__construct($name, $invoke = null): Creates the mw stack with a name and an optional invoker. The invoker will be passed along to mw\compose.
string getName(): returns the name of the middleware
callable getInvoke(): returns the current value set for invoke which could be null or a callable.
MwStack push($mw, $sort = 0, $name = null): Pushes a new middleware on the stack. The sort determines the priority of the middleware. Middleware pushed at the same priority will be pushed on like a stack.
MwStack unshift($mw, $sort = 0, $name = null): Similar to push except it prepends the stack at the beginning.
MwStack before($name, $mw, $mw_name = null): Inserts a middleware right before the given middleware.
MwStack after($name, $mw, $mw_name = null): Inserts a middleware right after the given middleware.
array shift($sort = 0): Shifts the stack at the priority given by taking an element from the front/bottom of the stack. The shifted stack entry is returned as a tuple.
array pop($sort = 0): Pops the stack at the priority given be taking an element from the back/top of the stack. The popped stack entry is returned as a tuple.
array remove($name): Removes a named middleware. The removed middleware is returned as a tuple.
array normalize(): Normalizes the stack into an array of middleware that can be used with mw\compose
mixed __invoke(...$params): Allows the middleware stack to be used as middleware itself.
Closure compose(callable $last = null): Composes the stack into a handler.
Generator getEntries(): Yields the raw stack entries in the order they were added.
MwStack static createFromEntries($name, $entries): Creates a stack with a set of entries. mw\stack internally calls this.