我如何使用PHP 5.3 Closures，比如我们在Ruby中使用Blocks

Question

How can I use PHP 5.3 Closures like We use Blocks in Ruby. I never used 'for' Loop in Ruby due to using Blocks with 'each' 'find_all' 'inject' Methods.

How can I use PHP 5.3 Closures like Ruby Blocks and say bye-bye to 'for' Loops :)

Like Between { and } is a Closure(or Block or Anonymous Function)

fruit = %w[apple banana orange]
fruit.each { |f| print "#{f}, " }

I do it in PHP this way,

$fruit = array('apple', 'banana', 'orange');
foreach ($fruit as $f) 
{
 print "$f, "; 
}

Is there a way to do this the Ruby way using PHP Closures as PHP 5.3 supports it.

Answer 1

If you are looking at using lambdas to iterate over a PHP array, there are certain functions that you could use to accomplish that. Better illustrate it, I used a wrapper class enum:

class enum {
    public $arr;

    function __construct($array) {
        $this->arr = $array;
    }

    function each($lambda) {
        array_walk($this->arr, $lambda);
    }

    function find_all($lambda) {
        return array_filter($this->arr, $lambda);
    }

    function inject($lambda, $initial=null) {
        if ($initial == null) {
            $first = array_shift($this->arr);
            $result = array_reduce($this->arr, $lambda, $first);
            array_unshift($this->arr, $first);

            return $result;
        } else {
            return array_reduce($this->arr, $lambda, $initial);
        }
    }

}


$list = new enum(array(-1, 3, 4, 5, -7));
$list->each(function($a) { print $a . "
";});

// in PHP you can also assign a closure to a variable 
$pos = function($a) { return ($a < 0) ? false : true;};
$positives = $list->find_all($pos);

// inject() examples
$list = new enum(range(5, 10));

$sum = $list->inject(function($sum, $n) { return $sum+$n; });
$product = $list->inject(function($acc, $n) { return $acc*$n; }, 1);

$list = new enum(array('cat', 'sheep', 'bear'));
$longest = $list->inject(function($memo, $word) {
        return (strlen($memo) > strlen($word)) ? $memo : $word; }
    );

That being said, closures in PHP aren't meant to replace the for loop nor do they behave like ruby blocks.