Bad Word Filter, how do I replace words by their length?

Question

I have this PHP Code, it generates random characters where there is a bad word:

$wordreplace = array (
  \"!\",
  \"#\",
  \"@\",
  \"&\",
  \"^\",
  \"$\",
         


        

Answer 1

for replace bad words in string you can use preg_replace_callbackto perform a regular expression search and replace using a callback.

below example replace all bad words with *

output :

PHP is a ***ular general-purpose scripting language that is especially suited to web *****opment.

<?php
header('Content-Type: text/plain');

// array of bad words to filter 
$badwords = array('pop','devel');

// strin to clean from bad words  
$text = 'PHP is a popular general-purpose scripting language that is especially suited to web development.';
// with /\w+/ regex we send each word to  replace_badwords function 
$text = preg_replace_callback('/\w+/', 'replace_badwords', $text);

echo $text;

// replace_badwords check if string has bad word then its replace with * char or not return otrginal word
function replace_badwords($ocr) {
  global $badwords;
  $newstr=false;
  foreach ($badwords as $key => $value) {

        $start = strpos($ocr[0],$value);
        if($start!== false){
            $length = strlen($value);
            $newstr = substr_replace($ocr[0],str_repeat("*",$length),$start,$length);
        }

        }

    return $newstr ? $newstr :  $ocr[0];

}

?>

Answer 2

You might be overthinking this. The whole first part of your code is meant to find a randomized replacement for the bad word. Only those last two lines matter, and you can replace them with:

$content = preg_replace_callback(
    $badwords,
    function ($matches) {
        return str_repeat('*', strlen($matches[0]));
    },
    $content
);

To make this work, though, you need to wrap your badwords in a 'capture group' like so:

$capture_badwords = [];
foreach ($word in $badwords) {
    $capture_badwords[] = "/(".$word.")/";
}

This should produce an array like this:

["/(abadword)/", "/(anotherbadword)/", "/(afourletterword)/", ... ]

preg_replace_callback lets you define a function with which you can manipulate the matched group.

Putting this together in an example:

$badwords = [ "/(dog)/", "/(cat)/", "/(here)/" ];
//"#\((\d+)\)#"
$phrase = "It is just dogs chasing cats in here.";

echo preg_replace_callback(
        $badwords,
        function ($matches) {
            return str_repeat('*', strlen($matches[0]));
        },
        $phrase
    );

Yields:

It is just ***s chasing ***s in ****.