Preg_replace whole word only

[empiresolutions]

Im trying to make a naughty word filter. It removes bad words fine, but instances where there is a bad word found in the text like "assist" and "asses" get caught in the filter as well. Strangely though if the sentence is: My asses to assist me." the clean version will read: My asses to ***ist me." It seems to clear the first use of the word in another word, but then blocks the rest. Any ideas? My script is below. Thanks.

 
function cleanWords($value) {
 
    /*   strip naughty words   */
    $bad_word_file = 'standards/badwords.txt';
    $strtofile = fopen($bad_word_file, "r");
    $badwords = explode("\n", fread($strtofile, filesize($bad_word_file)));
    fclose($strtofile);
 
    for ($i = 0; $i < count($badwords); $i++) {
        $wordlist .= str_replace(chr(13),'',$badwords[$i]).'|';
    }
    $wordlist = substr($wordlist,0,-1);
 
    $value = preg_replace("/\b($wordlist)\b/ie", 'preg_replace("/./","*","\\1")', $value);    
    return $value;
 
}
 
 

[Atli]

Hey.

If you print the $wordlist, does it look right?
I tested this by just creating the $wordlist manually and it seemed to work fine.

[empiresolutions]

yes $wordlist is correct. If it helps the wordlist is just over a 1000 words.

[philipwayne]

Use the space character with or conditions.

(\s|^)(badword1|badword2)(\s|$)

That checks for either a space before the word or if it is at the start of the screen. Then checks for either a space or the end of the line.

[empiresolutions]

i ended up finding that the word "a.s.s." was in my list. I think the dots were messing up the expression. For thos interested, this is my new code. Thanks for any suggestions to get it where it is.

$_SESSION[wordlist] = join("|", array_map('trim', file('standards/badwords.txt')));
 
function cleanWords($value) {
 
    global $_SESSION;
 
    $value = preg_replace("/\b($_SESSION[wordlist])\b/ie", 'str_repeat("*", strlen("\\1")) ', $value);    
    return $value;
 
}
 

[Atli]

Hey.
Glad you got it working.

However, I would consider using a different method. - Putting the whole thing into the session is very inefficient. The list remains constant for every user, and rarely changes (if ever) right? - If so, then compiling it for every user like that and storing it in separate sessions for each one is just doing two things: eating up resources and cluttering the sessions with duplicate data.

You would be far better of compiling the regular expression into a common file, shared between all users. - This is how I would do this. (Wouldn't usually make a ready-to-use code example, but since you already solved this on your own...)

<?php
define("BADWORDS_RAW_FILE", "/path/to/badwords.txt");
define("BADWORDS_EXP_FILE", "/path/to/badwords_expression.txt");
 
/**
 * Returns a regular expression that can be used to check
 * for "bad" words. Returns an expression in the format:
 *  - /\b(list|of|bad|words)\b/i
 */
function getBadWordsRegexp()  
{
    $regexp = "";
 
    // Try to fetch an existing expression.
    if(!file_exists(BADWORDS_EXP_FILE) || 
       filesize(BADWORDS_EXP_FILE) <= 0 ||
       ($regexp = file_get_contents(BADWORDS_EXP_FILE)) === false)
    {
        // Make sure the raw word list exists
        if(!file_exists(BADWORDS_RAW_FILE)) {
            trigger_error("The bad words file does not exists.", E_USER_ERROR);
            return false;
        }
 
        // Compile the regular expression
        $regexp = '/\b(' . join("|", array_map('trim', file(BADWORDS_RAW_FILE))) . ')\b/i';
 
        // Try to save it
        if(!is_writeable(BADWORDS_EXP_FILE) ||
           !file_put_contents(BADWORDS_EXP_FILE, $regexp)) 
        {
            trigger_error("Could not save badwords expression. Check file permissions.", E_USER_WARNING);
        }
    }
 
    // Return it
    return $regexp;
}
?>

Then you could use it like:

<?php
function cleanWords($value) {
    $regexp = getBadWordsRegexp();
    return preg_replace($regexp . 'e', 'str_repeat("*", strlen("\\1")) ', $value);
}
?>

P.S.
I have a couple of notes on your code, though.

• You don't need to import $_SESSION into functions using the global keyword. $_SESSION is a "super-global", which makes it available to you wherever you are in your code.
  
• All strings need to be quoted. That includes array keys. Which means that:
  

  // This
  $_SESSION[wordlist];
   
  // Should be
  $_SESSION['wordlist'];

  If you leave it out, PHP assumes it is a constant. Failing to find a constant, it prints a warning and uses it as a string (which is why it works, even thought it is technically an error.) - For future-compatibility and performance reasons (minor as they may be), it is best to just remember the strings.

[empiresolutions]

thanks Atli! your suggestions are much appreciated.