Exceptions...

factory.php

<?php

class ExceptionFactory implements ExceptionFactoryInterface {
    public function __invoke($msg = '') {
        return new \Exception($msg);
    }
}

int.php

<?php

interface ExceptionFactoryInterface {
    /**
     * @return \Exception
     */
    public function __invoke();
}

output

Throw new Exception: 2.838799
Throw $exception: 0.540748

run.php

<?php

$theThing = function(ExceptionFactoryInterface $factory) {
    throw $factory();
};

$sef = new ExceptionFactory;
$nef = new StacklessExceptionFactory;

echo "Throw new Exception: ";
$s = microtime(true);
for ($i = 0; $i < $t; $i++) {
    try {
        $theThing($sef);
    } catch (Exception $e) {
    }
}
printf("%0.6f\n", (microtime(true) - $s));

echo 'Throw $exception: ';
$s = microtime(true);
for ($i = 0; $i < $t; $i++) {
    try {
        $theThing($nef);
    } catch (Exception $e) {
    }
}
printf("%0.6f\n", (microtime(true) - $s));

stackless.php

<?php

class StacklessExceptionFactory implements ExceptionFactoryInterface {
    private $held;

    public function __construct() {
        $this->held = new \Exception;
    }

    public function __invoke() {
        return $this->held;
    }
}