The function trim don't cut the space

<?php
$rr = 'http://biodizionario.it/images/semafori/rr.gif';
$r =  'http://biodizionario.it/images/semafori/r.gif';
$g =  'http://biodizionario.it/images/semafori/g.gif';
$v  = 'http://biodizionario.it/images/semafori/v.gif';
$vv = 'http://biodizionario.it/images/semafori/vv.gif';

$filer = fopen("bio_format.txt", "w");
$file = fopen("bio.txt", "r");

while (!feof($file)) {
    $buffer = fgets($file, 4096);
    
    $pos = stripos($buffer,$rr);
    if ($pos) $s = "RR; ";
    $pos = stripos($buffer,$r);
    if ($pos) $s = "R; ";
    $pos = stripos($buffer,$g);
    if ($pos) $s = "G; ";
    $pos = stripos($buffer,$v);
    if ($pos) $s = "V; ";
    $pos = stripos($buffer,$vv);
    if ($pos) $s = "VV; ";
    
    $pos1 = stripos($buffer,'<b>');
    $pos2 = stripos($buffer,'</b>');
    $diff = $pos2 - $pos1;
    $start = $pos1 + 3;
    $rest = $diff - 3;
    $nome = substr($buffer, $start, $rest);
    $s = $s . $nome . ";" ;
    
    $pos1 = stripos($buffer,'</b>');
    $pos2 = stripos($buffer,'<br />');
    $diff = $pos2 - $pos1;
    $start = $pos1 + 4;
    $rest = $diff - 4;
    $descr = substr($buffer, $start, $rest);
    $descr1 = trim($descr);
    $s = $s . $descr1 . ";" . "\r\n";
    
    fwrite($filer, $s);
}
fclose($file);
fclose($filer);
?>

RR; 1-NAPHTHOL;      colorante capelli;
RR; 1,2,4-BENZENETRIACETATE;      colorante capelli;
RR; 1,3-BIS-(2,4-DIAMINOPHENOXY)PROPANE;      colorante capelli;
RR; 1,5-NAPHTHALENEDIOL;      colorante capelli;