<?php
 
$badWords = array('palavra1', 'palavra2', 'palavra3');
 
$string = "A palavra1 é igual a palavra2 que é diferente da palavra3";
$matchFound = preg_match_all(
                "/\b(" . implode($badWords,"|") . ")\b/i", 
                $string, 
                $matches
              );
 
$p = array();
if ($matchFound > 0) {
  $words = array_unique($matches[0]);
  foreach($words as $word) {
    $p[] = $word;
  }
  echo '<div class="notice notice-danger">A historia contém palavras censuradas, não poderá ser publicada. (';
  print_r($p);
  echo ' ) </div>';
 
  die();
}

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