errore query

[prinzart]

mi compare questo errore:

Fatal error: Call to undefined function fetch() in /web/htdocs/www.sito.it/home/directory/prova.php on line 38

il codice è questo, ma non capisco dov'è che sbaglio:

<?php
   $maxSize = 20; //dimensione massima in pixel
    $minSize = 8; //dimensione minima in pixel

     $query_1 = "SELECT count(*) as Num, id_art_marca FROM c_art_articolo GROUP BY id_art_marca";
       $mysql_query_1=mysql_query($query_1, $conn);
       
       
    $tag = array();
    while($row = fetch($mysql_query_1))
        $tag[$row['id_art_marca']] = $row['Num'];
   
    $max = max($tag);
   
    $out="<div style='width:100px;'>\n";
    foreach($tag as $key => $value)
        $out.="<span style='font-size:".getSizeFromPerc(($value/$max)*100, $maxSize, $minSize)."px' title='$value Argomenti'>$key</span>\n";
   
    $out.="</div>";
   
    echo $out; //stampo tutto
   
   
    function getSizeFromPerc($percent, $maxSize, $minSize) {
        $step = ($maxSize - $minSize) / 10;
       
        if ($percent >= 95)
            $size = $maxSize;
        else if ($percent >= 70)
            $size = $minSize + $step*8;
        else if ($percent >= 60)
            $size = $minSize + $step*7;
        else if ($percent >= 50)
            $size = $minSize + $step*6;
        else if ($percent >= 40)
            $size = $minSize + $step*5;
        else if ($percent >= 30)
            $size = $minSize + $step*4;
        else if ($percent >= 20)
            $size = $minSize + $step*3;
        else if ($percent >= 10)
            $size = $minSize + $step*2;
        else if ($percent >= 5)
            $size = $minSize + $step;
        else
            $size = $minSize;
           
        return $size;
    }
?>