Ejemplo basico de closures en PHP 5.4

closures.php

<?php
class Calc {
  public function mult($by = 1) {
      return function($number) use($by) {
        return $by * $number;
      };
  }
}

$calc = new Calc;
$multBy10 = $calc->mult(10);
echo $multBy10(5); // 50

$multBy34 = $calc->mult(34);
echo $multBy34(8);  //  272