How to read data and send it to another PHP page?

Hello. You can help me I need that when the user click on register another page appears but it can vary if there are several Cards (I am using Materialize) and must show different data according to the group name like 3S1-IS, 1S1-CIV.

As I do so that the click on register read the header data and send them to another php page to later show the necessary.

This is my PHP code

<?php 
    $Conex=conectar();

    $query="SELECT * FROM prof_clases WHERE Nombre_Usuario='". $_SESSION["usuario_valido"] ."'";

    $resultado= ejecutar($query,$Conex);
    if(mysql_num_rows($resultado)>0)
    {

     $num=mysql_num_rows($resultado);
     for ($i=0; $i < $num; $i++) 
     { 
       $fila=mysql_fetch_array($resultado);

      echo " 
      <div class='col s3'>
      <div class='card teal darken-2'>
      <div class='card-content white-text'>
      <span class='card-title'>". $fila["Nombre_Grupo"] ."</span>
      <p>Carrera: ". $fila["Nombre_Carrera"] ."</p>
      <p>Año: ". $fila["Anio"] ."</p>      
       </div>
      <div class='card-action'>

      <a href='registrar.php'>Registrar notas</a>
      </div>
      </div>
      </div>
      ";


    }
  }

  ?>