The first parameter $array can be also be functions, which produces very interesting and powerful result, which can be used to make an union of middlewares.
<?php
$f1 = function($x, $f){
echo 'middleware 1 begin.'.PHP_EOL;
$x += 1;
$x = $f($x);
echo 'middleware 1 end.'.PHP_EOL;
return $x;
};
$f2 = function($x, $f){
echo 'middleware 2 begin: '.PHP_EOL;
$x += 2;
$x = $f($x);
echo 'middleware 2 end.'.PHP_EOL;
return $x;
};
$respond = function($x){
echo 'Generate some response.'.PHP_EOL;
return $x;
};
$middlewares = [$f1, $f2];
$initial = $respond;
$foo = array_reduce($middlewares, function($stack, $item){
return function($request) use ($stack, $item){
return $item($request, $stack);
};
}, $initial);
$x = 1;
echo $foo($x);
?>
//output:
middleware 2 begin:
middleware 1 begin.
Generate some response.
middleware 1 end.
middleware 2 end.
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