$_Files upload

<?php

    $month = date('F');
    $day = date('j');
    $year = date('Y');
     $file_type = "";
      $file_name = "";
      $file_size = "";
      $file_tmp = "";
      $file_type = "";
      $file_namex = NULL;


   if(isset($_FILES['doc'])){
      $tag = trim($_POST['tag']);
      $errors= array();
      $file_name = $_FILES['doc']['name'];
      $file_size = $_FILES['doc']['size'];
      $file_tmp = $_FILES['doc']['tmp_name'];
      $file_type = $_FILES['doc']['type'];
      $file_ext=strtolower(end(explode('.',$_FILES['doc']['name'])));

      $query="SELECT * FROM doc_tbl WHERE filename='$file_name'";
        $result=mysql_query($query);
        $n = 1;
        if(mysql_num_rows($result)==1){
    while(mysql_num_rows($result)==1){
        $file_namex = "(".$n.")".$file_name;
        $query="SELECT * FROM doc_tbl WHERE filename='$file_namex'";
        $result=mysql_query($query);
        $n++;

        }
        $file_name = $file_namex;
        }
      $expensions= array("pdf","doc","docx","docm","dot","xlt","xml","xlsx","xls","ppsx","ppt","pptm","pptx","psd");

      if(in_array($file_ext,$expensions)=== false){
         $errors[]="File extension not allowed";
      }

      if($file_size > 750097152) {
         $errors[]='File size must be excately 750 MB';
      }

      if(empty($errors)==true) {
         move_uploaded_file($file_tmp,"doc/".$file_name);
            mysql_query("INSERT INTO doc_tbl(filename, name, size, month, day, year, type, tag)
            VALUES ('$file_name', '$user', '$file_size', '$month', '$day', '$year', '$file_type', '$tag')");
         echo "Success";
      }else{


         print_r($errors);
      }
   }
?>
<html>
   <body>

      <form action = "" method = "POST" enctype = "multipart/form-data">
      <table><tr><td class="td">
         <input type = "file" name = "doc" class="btnblue2"/></td></tr>
        <tr><td class="td"> TAG:<select id=cmbteacher name=tag class=box>
        <?php
    $result1 = mysql_query ("SELECT * FROM tags_tbl");
    while($row = mysql_fetch_array($result1)){
      ?>


    <option value="<?php echo $row['id']; ?>"><?php echo $row['service']; ?> : <?php echo $row['tag']; } ?></option>

</select>

         <input type = "submit" class="btnblue"  name="post"/></td></tr></table>
        <table>
        <tr><td class="td2">Sent file:</td><td class="box"> <?php echo $file_name;  ?></td></tr>
         <tr ><td class="td2">  File size:</td><td class="box">  <?php echo $file_size;  ?></td></tr>
        <tr><td class="td2"> File type:</td><td class="box">  <?php echo $file_type; ?></td></tr>
        </table>


      </form>