need to fix a bug. Invalid utf8 character string: '\xF3'

Hi i need to fix a bug here. i need someone to help me fix it so i can continue. $requestId = base64_decode($_GET['request_id']); i get this error code: need to fix a bug. Invalid utf8 character string: '\xF3' this is the full script: include "[login to view URL]"; $requestId = base64_decode($_GET['request_id']); $sql = mysql_query("SELECT id,images FROM checklists WHERE id = $requestId ORDER BY id DESC") or die(mysql_error()); $results = mysql_fetch_array($sql); // count the output amount $imagesNames = $results['images']; if(!empty($_FILES)){ $imagesString = ''; $target_dir = "upload/"; $i = 0; $u = 0; $imgArr = array(); foreach($_FILES['fileToUpload']['name'] as $file){ $fileName = time().basename($file); $target_file = $target_dir . $fileName; $imagesNames .= '&&&'.$fileName; $imageFileType = strtolower(pathinfo($target_file,PATHINFO_EXTENSION)); if($imageFileType != "jpg" && $imageFileType != "png" && $imageFileType != "jpeg" && $imageFileType != "gif" ) { }else{ move_uploaded_file($_FILES['fileToUpload']['tmp_name'][$i], $target_file); $imgArr [] = $fileName; } $i++; } } if($imagesNames != ''){ $result = mysql_query("UPDATE checklists SET images='$imagesNames' WHERE id = $requestId" ) or die(mysql_error()); $submitted = 1; }