codginator search query

You cannot rely on undefined variables in PHP.  You must test to see if they exist and contain useful values before you use them in a script.
http://php.net/manual/en/function.isset.php

In case you're new to PHP and want to get a foundation (necessary for working on PHP internals of CodeIgniter or any other framework) this article might help.
https://www.experts-exchange.com/Web_Development/Web_Languages-Standards/PHP/A_11769-And-by-the-way-I-am-new-to-PHP.html

I think you get that error when you load the page before to submit your query: this means that the chek

if($this->input->post('submit'))

fails and then the variable $dt['val'] is never filled and when the view is loaded it raises the error. Put a check in the View:

<?php 
if (isset($val))
{
foreach ($val as $va){?>
<?php echo  $va['namehost'];?><br>
<?php  }
}?>

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And the error will go away :-)

THANKS SIR ,
  FOR YOUR SUPPORT BUT I THINK THAT I M MAKING PROBLEM MOST ON
MODEL (I THINK THATS NOT EXACT QUERY AS CI WANT)
THEN SMALL ON CONTROLLER.

orry, have you tried to do what I said?

About your model, here you'll find the info you need:https://ellislab.com/codeigniter/user-guide/database/active_record.html

 public function mgetclinds($a,$b,$c,$d,$e,$f,$g,$h,$i,$j)
    {
         $array = array(
              'state' => $f,
              'city' => $g,
              'area' => $h, 
              'cate' => $i,
              'for' => $j
         );
        $this->db->like($array);
        $query=$this->db->get($a,$b,$c,$d,$e);
        return $query->result_array();
    }?>

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Oh sorry
yes sir i apply checck method from this 2 error are gone

but after pushing submit button

these error are come

* all errors on same page

really thanks sir that you are helping me.
error1.png
error2.png

I strongly discourage you from hiding errors, warnings and even notices: if there is an issue, then solve it now. Hiding it just grant you to accumulate an incredible amount of small issues which, all together, can make your life a nightmare.
That error is probably because the creation of $dt variable depends on the submission of values. If the user doesn't submit anything, that is if you access the page directly typing in the adddress bar of your browser www.yourdomain.com/controller_name/extra1, then the $dt array doesn't exsist, but you pass it to the view anyway: from here the warning. Do this instead:

<?php  //ON CONTROLLER//
public function extra1()
        {
          $dt['val'] = '';
          if($this->input->post('submit'))
                {
                    $selected1=$this->input->post('state');
                    $selected2=$this->input->post('city');
                    $selected3=$this->input->post('area');
                    $selected4=$this->input->post('cate');
                    $selected5=$this->input->post('for');
         
        
        $dt['val']=$this->demomod->mgetclinds('reg',$selected1,$selected2,$selected3,$selected4,$selected5);
          // echo "$selected1,$selected2,$selected3,$selected4,$selected5";
   
          }  
            
          $this->load->view('extra1',$dt); 

       }
    ?> 

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Yes sir I do this as you guide me.

Thanks.