php에서 sql 수정시 문자열 합치기가 잘 안되네요ㅠㅠ

<?ini_set("display_errors",0);@header('Content-Type: text/html; charset=euc-kr');include_once $_SERVER['DOCUMENT_ROOT']."/lib/db.php";$seq = $_POST['seq'];$Act = $_POST['Act'];$project_name = $_POST['project_name'];$target_cnt = $_POST['target_cnt'];$reg_date = $_POST['reg_date'];$sql = "select seq from tbl_project where project_name='".$project_name."'";$row = mysql_fetch_array(mysql_query($sql));if($row['seq']){    ?>  <script type="text/javascript">  alert('동일한 제품정보가 있습니다!');  location.href="main_sub003_project_list.php";  </script>  <?  exit;}switch($Act){  case 'write':   $sql= "insert into tbl_project(project_name,target_cnt,reg_date) values('".$project_name."',".$target_cnt.",now())";   $retVal = mysql_query($sql);   break;  case 'modify':   $project_name=$reg_date."".$project_name;   $sql = "update tbl_project set project_name='".$project_name."',target_cnt=".$target_cnt." where seq=".$seq;   $retVal = mysql_query($sql);   break;}if($retVal){?><script type="text/javascript">alert('처리 완료!');location.href="main_sub003_project_list.php";</script><?}else{?><script type="text/javascript">alert('처리 실패!!');location.href="main_sub003_project_list.php";</script><?}?>