Word Replacer

Hi,

I have a function which i use to replace words in a sentence.

The issue i am having is it is replacing a section of a word e.g. acknowledge the word know might be replaced with understand so we would be left with acunderstandledge which does not make sense.

The Mysql tabel is made up like this

Original work Replacements
know understand, be aware of

How do i change the function below so that it only replaces exact full word matches rather than i partial?

Function below

function change_text($description){


    $result = mysql_query("SELECT original, replacement FROM `text_replacements`") or die(mysql_error());
    while(list($original, $wordlist) = mysql_fetch_array($result)) {
   
        // Make an array out of each word list and shuffle it, so we get something new on each run
        $word = explode(', ', $wordlist);
                   
        // Magic happens here
        $tmp = preg_split('/[\s]+/', trim($description));
        $c = count($tmp);
        for($i = 0; $i < $c; $i++){   
       
            // Remove right whitespace       
            $tmpword = rtrim($tmp[$i]);
           
            // Save var with original text for replace function later
            $search_text = $tmpword;
            $extra = '';
            shuffle($word);   
           
            // If tmpword starts uppercase, make it lowercase to compare. Replacement will be turned uppercase
            if (ctype_upper(substr($tmpword, 0 , 1))) {
                $tmpword = strtolower($tmpword);                       
                $replacement = ucfirst($word[0]);
            }
            else { $replacement = $word[0]; }
       
            // If word end with .,?! remove from tmpword, so we can use it in the next check
            // create var to append extra signs again
            if(substr($tmpword, -1) == ',' || substr($tmpword, -1) == '.' || substr($tmpword, -1) == '?' || substr($tmpword, -1) == '!') {
                $extra = substr($tmpword, -1);
                $tmpword = substr($tmpword, 0, -1);
            }   
           
            // after all checks (lowercase, remove extra chars from tmpword)
            // check if this reduced word is in our replace list
            // If it is replace all
            if(in_array($tmpword, $word)) {
                $description = str_replace($search_text, $replacement.$extra, $description);
            }           

        }       

    }

    return nl2br(preg_replace('/([.!?]\s*\w)/e', "strtoupper('$1')", ucfirst(strtolower($description))));



}

Code (markup):