class.acl.php

<?php

class ACL
{
    private $actions;
    private $perm;
    private $eval = 0;


    /**
     * Constructor that sets the permissions code passed to it.
     * @param integer $perm The permissions code that will be tested against. It
     *   is optional and not needed when only using the class to generate a new
     *   permissions code.
     */
    public function __construct($actions, $perm = 0)
    {
        $this->actions = $actions;
        $this->perm = intval($perm);
    }


    /**
     * Checks wether or not the permissions code passed to the constructor will
     * allow the provided action.
     * @param  string  $action The action to be tested for
     * @return boolean         Wether or not the action may be performed
     */
    public function hasPermission($action)
    {
        if(in_array($action, $this->actions)){
            return $this->testPermission($this->perm, $action);
        }else{
            return $this->invalidAction();
        }
    }


    /**
     * Adds an action to the eval property when generating a new permissions
     * code.
     * @param string $action The action that should be allowed.
     */
    public function addPermission($action)
    {
        if(!$this->testPermission($this->eval, $action)){
            $this->eval += $this->getKey($action);
        }
    }


    /**
     * Removes an action to the eval property when generating a new permissions
     * code.
     * @param string $action The action that should not be allowed.
     */
    public function removePermission($action)
    {
        if($this->testPermission($this->eval, $action)){
            $this->eval -= $this->getKey($action);
        }
    }

    /**
     * Returns the permissions code generated by adding allowed actions via the
     * addPermission method.
     * @return int   The new permissions code.
     */
    public function evaluate()
    {
        return $this->eval;
    }


    /**
     * Returns an array of possible actions.
     * @return array All possible actions
     */
    public function getActions()
    {
        return $this->actions;
    }


    /**
     * Checks if the provided action is alloed when using the provided
     * permissions code.
     * @param  int    $permCode A permissions code.
     * @param  string $action   The action to test for.
     * @return bool             Wether or not the action should be allowed.
     */
    private function testPermission($permCode, $action)
    {
        $key = $this->getKey($action);
        return ( ($permCode & $key) == $key);
    }


    /**
     * Gets the bitmask value based on an actions position in the array of possible actions.
     * @param  string $action The action to look up
     * @return int            The bitmask value
     */
    private function getKey($action)
    {
        return pow(2, array_search($action, $this->actions));
    }


    /**
     * The response when an action that's not in the list of possibilities is
     * tested.
     * @return bool  Always returns false.
     */
    private function invalidAction()
    {
        throw new Exception('INVALID ACTION');
        return false;
    }

}

?>