php - How to assign a value only for first time -

in web system have 3 files database.php , functions.php, dashboard.php

this how dashboard.php file looks like

             <?php                  $i=null;                 if(isset($_post['next']))                 {                     $i=getquizes($i);                 }              ?>             <form method="post" action="<?php echo $_server['php_self']; ?>">                 <input name="next" value="next" type="submit">             </form> 

functions.php below

function getquizes($quizno) {     if($quizno==null)     {         $quizno=0;     }     include_once('database.php');     $sql = "select * quiz limit ".$quizno.",1";     $result = $conn->query($sql);     while($row=$result->fetch_assoc())     {         echo $row['question'],$quizno;     }     $quizno++;     return $quizno; } 

when clicked submit button data go functions.php file , comes dashboard.php again $i becomes null. can assign null first time.if yes,how can that.

store $i in session , load in every request, if it's not set in $_session set $i null

<?php    $i = isset($_session['next']) ? $_session['next'] : null;    if(isset($_post['next']))    {        $i = getquizes($i);        $_session['next'] = $i;    }?>    <form method="post" action="<?php echo $_server['php_self']; ?>">         <input name="next" value="next" type="submit">    </form>