gistfile1.php

<?php

class TrainRider
{
    static $num_riders = 0;

    public $times_ridden = 0;

    public function rideTrain()
    {
        ++$this->times_ridden;
        ++self::$num_riders;
    }
}

// Create two new train riders
$tom = new TrainRider;
$john = new TrainRider;

$tom->rideTrain(); // Go to work
$tom->rideTrain(); // Come home

$john->rideTrain(); // Go to his parents' house for the weekend

// Output information about the train and its riders
echo "Tom has ridden the train ", $tom->times_ridden, " times.<br />",
    "John has ridden the train ", $john->times_ridden, " times.<br />",
    "The train has had a total of ", TrainRider::$num_riders, " riders.";

// Output is:
// Tom has ridden the train 2 times.
// John has ridden the train 1 times.
// The train has had a total of 3 riders.