Remove doublon from a text, first break by '.' then by ',' and after build a text without doublons

remove doublon from text

$content = "";

$content = preg_replace('/\n\r|\r\n|\n|\r/','', $content);
$content = preg_replace('/\s+/', ' ',$content);
$content = preg_replace('/<br \/><br\/><br\/><br\/>              /',' ', $content);
$content = str_replace('&nbsp;','',$content);
$content = str_replace('&#39;','\'',$content);
$content = str_replace('&agrave;','à',$content);
$content = str_replace('&eacute;','é',$content);
$content = preg_replace('/\n\r|\r\n|\n|\r/','', $content);
 		
$parts = explode('.',$content);

$sentences = array();
$sentences2 = array();
$sentences = array_values(array_unique($parts));

foreach($sentences as $sentence){
    $parts2[] = explode(',',$sentence);
}

foreach($parts2 as $parts21){
    foreach($parts21 as $parts211){
        $sentences2[] = $parts211;
    }    

}
$sentences2 = array_values(array_unique($sentences2));

foreach($sentences2 as $sentences21){ 
    echo $sentences21;
    echo '. ';
}