I have 3 variable mat , follow , not 
only one can have value at a time what I want if any of the variables has value it should be updated in msg

this is my logic

```
<?php     
    $mat = $this->input->post('mater_mesaage') ;
    $folow = $this->input->post('follow_message') ;
    $not = $this->input->post('not_inst_comment') ;     
    if (isset($mat)){
        echo "Mat";
        $msg = $mat  ;
    } 
    if (isset($folow )) {
        echo "folow" ;
       $msg = $folow ;
    }
    if (isset($not)){
        echo "not" ;
        $msg = $not ;
    }
    echo $msg ;
?>

```