soal pipeline

<?php
class Pipeline
{
    public static function make_pipeline(...$funcs)
    {
        return function($arg) use ($funcs)
        {
            foreach($funcs as $list)
            {
                if(!isset($value))
                {
                    $value = $list($arg);
                }else
                {
                    $value = $list($value);
                }
            }
            
            return $value;
        };
    }
}

$fun = Pipeline::make_pipeline(
                                function($x) { return $x * 3;}, 
                                function($x) { return $x + 1;},
                                function($x) { return $x / 2;}
                                );

echo $fun(3); # should print 5