CWhitelist.php

<?php
/**
 * Act as whitelist (or blacklist).
 *
 */
class CWhitelist
{
    /**
     * Array to contain the whitelist options.
     */
    private $whitelist = array();



    /**
     * Set the whitelist from an array of strings, each item in the
     * whitelist should be a regexp without the surrounding / or #.
     *
     * @param array $whitelist with all valid options,
     *                         default is to clear the whitelist.
     *
     * @return $this
     */
    public function set($whitelist = array())
    {
        if (!is_array($whitelist)) {
            throw new Exception("Whitelist is not of a supported format.");
        }

        $this->whitelist = $whitelist;
        return $this;
    }



    /**
     * Check if item exists in the whitelist.
     *
     * @param string $item      string to check.
     * @param array  $whitelist optional with all valid options, default is null.
     *
     * @return boolean true if item is in whitelist, else false.
     */
    public function check($item, $whitelist = null)
    {
        if ($whitelist !== null) {
            $this->set($whitelist);
        }
        
        if (empty($item) or empty($this->whitelist)) {
            return false;
        }
        
        foreach ($this->whitelist as $regexp) {
            if (preg_match("#$regexp#", $item)) {
                return true;
            }
        }

        return false;
    }
}