PHP5 Basic Spam Class

<?php
/**
 * Basic spam class for PHP5. Aids in determining whether a
 * string is spam using several factors.
 *
 * @package        Spam
 * @author         David Parr <[email protected]>
 * @copyright      Copyright (c) David Parr, 2008
 */

class Spam
{
    // Configuration
    protected $config;
    
    // Bad words that we don't want in the string
    protected $bad_words;
    
    /**
     * Constructor. Sets configuration.
     *
     * @param array Configuration
     * @param array Bad words like 'shit', 'faggot'
     * @return void
     */
    public function __construct($config, $bad_words)
    {
        $this->config = $config;
        $this->bad_words = $bad_words;
    }
    
    /**
     * Performs several tests on a string to help
     * determine whether or not it is spam.
     *
     * @param string String we are checking
     * @return bool
     */
    public function check($str)
    {
        // Check the length of the string isn't too short, or long..
        $length = strlen($str);
        if($length < $this->config['min_length'] OR $length > $this->config['max_length'])
        {
            return false;
        }
        
        // Check the string is standard text (only letters, numbers, whitespace, dashes and periods.
        if( ! preg_match('/^[-\pL\pN\pZ_.!?]++$/uD', $str))
        {
            return false;
        }
        
        // Count the number of anchor links found in the string.
        preg_match_all('#(<a href|\[url|http:\/\/)#i', $str, $matches, PREG_PATTERN_ORDER);
        if(count($matches[0]) > $this->config['max_links'])
        {
            return false;
        }
        
        // I always like to cleanup after myself :D
        unset($matches);
        
        // Grammar check?
        if($this->config['grammar_check'])
        {
            // First letter should always be capitalized
            if($str[0] > 'a')
            {
                return false;
            }
            
            // Shouldn't be no more than 2 repetitive characters in any word. Very few words have more.
            // This is ugly but it does work. If you know of any other way please let me know.
            // This is useful for stopping idiots entering things like "hiiiiii" or "you smeeeeelll!!!!" :o
            $words = explode(' ', $str);
            $found = false;
            foreach($words as $word)
            {
                // The length of the word should be greater than 1 if its not an a or a number
                // This prevents things like U and R
                if(strlen($word) < 2 AND strtolower($word) != 'a' AND ! is_numeric($word))
                {
                    $found = true;
                    break;
                }
                
                $chars = explode("''", $word);
                $chars_count = array();
                foreach($chars as $char)
                {
                    if($chars_count[$char]++ > 2)
                    {
                        $found = true;
                        break;
                    }
                }
            }
            
            unset($words);
            unset($chars);
            unset($chars_count);
            
            if($found)
            {
                return false;
            }
        }
        
        // Check for any bad words.
        foreach($this->bad_words as $bad_word)
        {
            if(stripos($str, $bad_word) !== FALSE)
            {
                return false;
            }
        }
        
        // If we got here then everything is fine ;)
        return true;
    }
}

<?php

require_once('classes/Spam.php');

$config = array(
    'min_length'    => 10,
    'max_length'    => 255,
    'max_links'     => 0,
    'grammar_check' => true
);

// Replace these with much worse words lol
$bad_words = array('bad', 'terrible', 'awful');

$spam = new Spam($config, $bad_words);

$str = 'Hi everybody how are you!?'; // Will pass the check

$result = $spam->check($str);

if($result)
{
    echo 'String contains no spam';
}
else
{
   echo 'String does contain spam';
}

// TESTS

$str = 'Hello'; // Is too short so would fail
$str = 'http://games.com'; // Fails because of link

// If we have grammar check on the following will fail
$str = 'hi everyone how are you?'; // First letter isn't capitalized.
$str = 'hiiiii'; // Repetitive
$str = 'Hey u r idiot'; // Fails because of u and r
?>