PHP: Static Properties and Methods

Static Property:

<?php

class Automobile {
  public static $colorRed = "red";
}

echo Automobile::$colorRed;

A Class can use the keyword self to reference itself within a static method.

<?php

class Automobile {
  private static $colorRed = "red";

  public static function getColorRedName() {
    return self::$colorRed;
  }
}

echo Automobile::getColorRedName();