如何检查文件是否已经上传到php codeigniter [重复]

Question

This question already has an answer here:

• Codeigniter “file_exists($filename)” 1 answer

i have to upload a file and insert the data into tables.i am done with that part. now,i want to check whether the file has been already uploaded or not. if so,alert should be thrown.

    if(isset($_POST["submit"]))
    {
    if($_FILES['file']['name'])
    {
        $filename = explode(".", $_FILES['file']['name']);
        $a=$filename[0];
        foreach($a as $b){
        if($b==$filename[0]){
                            echo"file already uploaded";
                            }
                          }
     }
   }

</div>

Answer 1

             if($filename[1] == 'csv')
                                    {

                                         $fp = fopen($_FILES['file']['tmp_name'],'r') or die("can't open file");
                                         $a=$filename[0];
                                         echo $a;
                                         $query1 = $this->db->query("SELECT * from table WHERE table.filename='".$a."'");
                                         $b=$query1->num_rows();
                                         if($b>0)

                                         {
                                            echo "<script type='text/javascript'>alert('FILE ALREADY BEEN UPLOADED')</script>";
                                         }
              else{
                  }