How to check specific words in a textarea?

[Marco Langes]

Hello,
first of all: Excuse me for some bad English you might experience during the reading of this.

So I made this form with an textarea, people can write a comment in here but I wanted to create something that my function counts specific words in it and says:
Word 1: 12 times
Word 2: 3 times
etc
etc

Code of what I have so far (I'm still a beginner in PHP):

$commentaar = trim($_POST['commentaar']);
 
function commenteva($commentaar)
    {
        global $commentaar;
        $commentaar = nl2br($commentaar); //newlines    
 
        $positive = array("goed", "top", "beste"); //Positive words
        $negative = array("slecht", "kut", "beter", "zuigt", "haat"); //Negative words
 
        $plengte = strlen($positief);
        $nlengte = strlen($negatief);
 
        echo ("<br />Aantal positieve woorden: " . $plengte);
        echo ("<br />Aantal negatieve woorden: " . $nlengte);
 
            if($plengte > $nlengte)
            {
                echo("<br />Commentaar is positief");
            }
            elseif($nlengte > $plengte)
            {
                echo("<br />commentaar is negatief");
            }
            else
            {
            echo("<br />commentaar is neutraal");
            }
    }
 
 

I just can't get it to work, each try I get different errors, I hope I am clear enough.

Thanks

[JKing]

Have a look at this function.
PHP preg_match_all()

It checks for a pattern inside a string and returns the number of matches.