//$sql_if_exist_up='UPDATE '.$tbl_message.'SET msg_status=5 WHERE user_sender_id='.$user_id.' AND user_receiver_id='.$friend_id.' WHERE msg_status=5';
$sql_if_exist_up='UPDATE '.$tbl_message.'SET msg_status=5, set content = '.$message_content.' WHERE id='.$row_if_exist['id'].'';
$sql_if_exist_up='UPDATE '.$tbl_message.'SET msg_status=5, content = "'.$message_content.'" WHERE user_sender_id='.$user_id.' AND user_receiver_id='.$friend_id.' AND msg_status = 7 ';
//$sql_if_exist_up='UPDATE '.$tbl_message.'SET msg_status=5, set content = '.$message_content.' WHERE id='.$row_if_exist['id'].'';