How to Export Mysql database Using php script method-1

<?php
function export_database_tables($host,$user,$pass,$name,  $tables=false, $backup_name=false )
{
    $link = mysqli_connect($host,$user,$pass,$name);
      if (mysqli_connect_errno()){
            echo "ConnecttError: " . mysqli_connect_error();
      }
     mysqli_select_db($link,$name);  mysqli_query($link,"SET NAMES 'utf8'");
     $queryTables = mysqli_query($link,'SHOW TABLES');

        while($row = mysqli_fetch_row($queryTables)) {
                 $target_tables[] = $row[0];
         }

       if($tables !== false) {
            $target_tables = array_intersect( $target_tables, explode(',',$tables));
        }

      $content='';    //start cycle
       foreach($target_tables as $table){
           $result = mysqli_query($link,'SELECT * FROM '.$table);
           $fields_amount = mysqli_num_fields($result);
           $rows_num=mysqli_num_rows($result);
           $row2= mysqli_fetch_row(mysqli_query($link, 'SHOW CREATE TABLE '.$table));
           $content    .= "\n\n".$row2[1].";\n\n";
            for ($i = 0; $i < $fields_amount; $i++) {
                     $st_counter= 0;
                     while($row = mysqli_fetch_row($result)) {
                      //when started (and every after 100 command cycle)
                       if ($st_counter%100 == 0 || $st_counter == 0 )  {
                            $content .= "\nINSERT INTO ".$table." VALUES";
                       }
                $content .= "\n(";
                for($j=0; $j<$fields_amount; $j++)  {
                    $row[$j] = str_replace("\n","\\n", addslashes($row[$j]) );
                    if (isset($row[$j])) {
                      $content .= '"'.$row[$j].'"' ;
                    } else {
                           $content .= '""';
                    }
                    if ($j<($fields_amount-1)) {
                          $content.= ',';
                    }
                }
        $content .=")";
        //every after 100 command cycle [or at last line] ....p.s. but should be inserted 1 cycle eariler
        if ( (($st_counter+1)%100==0 && $st_counter!=0) || $st_counter+1==$rows_num) {
                   $content .= ";";
        } else {
                 $content .= ",";
         }
         $st_counter=$st_counter+1;
     }
  }
    $content .="\n\n\n";
}

    //save file
    $backup_name = $backup_name ? $backup_name : $name."___(".date('H-i-s')."_".date('d-m-Y').")__rand".rand(1,11111111).".sql";

      header('Content-Type: application/octet-stream');
      header("Content-Transfer-Encoding: Binary");       
      header("Content-disposition: attachment; filename=\"".$backup_name."\"");
      echo $content; exit;
}

//pass hostname=localhost, username=root, password="",databasename=wpdb
export_database_tables("hostname","username","password","databasename");

?>