Using $_POST value to as input on a new form

Question

I have an initial form with a single input and a submit. The options are gotten from a DB column 'clinics'. The user selects a clinic and submits by hitting NEXT.

1. The submitted $_POST value goes into the variable $clinic,
2. The $clinic variable is used to query the DB and get the $clinic_hours variable.
3. The user is then redirected to a new form with a text input prefilled with the $clinic value and with a label that says "clinic: General Hospital available hours: 7.4", which is $clinic and $clinic_hours.
4. The user fills the rest of the form and submits, but this causes the 2 variables to become undefined, and the form cannot be submitted. Does anyone know how to retain the $_POST values so I can submit them in a form?

This is my code:

form 1:

<form action="session.php" method="POST">      

    <select id="clinic" name="session_clinic">      

          <?php              
          while ( $row = mysqli_fetch_assoc($get_org_query) )                           
            {                      
               echo '<option 
       value="'.$row['name'].'">'.$row['name'].'</option>';                                
            }                                                 
          ?> 
       </select>

          <input type="submit" id="clinic_submit" 
          name="clinic_submit" value="Next">                         
</form>  

form 2:

 <form action="session.php" method="POST">  

    <label for="session_clinic" class="clinic_label">Clinic: <?php echo 
     $clinic ?> (Available: <?php echo $clinic_hours ?> hours)</label>
          <br>            

          <input type="text" id="session_clinic" 
       class="session_clinic" name="session_clinic" value="<?php 
        echo $clinic ?>">              

          <input type="date" name="session_date">

          <input type="text" id="session_duration" 
          class="duration" name="session_duration">

          <textarea name="session_note" id="session_note" cols="56" rows="7"></textarea>                          

          <input type="radio" name="status" value="Billable"> Billable<br>
          <input type="radio" name="status" value="Not Billable"> Not Billable<br>

          <input type="submit" name="session_submit" value="Submit">
</form>      

Answer 1

You can use hidden inputs to pass the values in the second form:

<input type="hidden" name="session_clinic" value="<?php echo $clinic; ?>">

As long as they have the same name as the first form then you should have access to the values again in the $_POST array.

Answer 2

In the second form you should create hidden fields and send $clinic and $clinic_hours.

 <input type="hidden" name="clinic" value="<?php echo $clinic; ?>">
 <input type="hidden" name="clinic_hours" value="<?php echo $clinic_hours; ?>">