public function getAlumn()
 {
     return AlumnData::getById($this->alumn_id);
 }
<?php

if (count($_POST) > 0) {
    $user = new AlumnData();
    $user->name = $_POST["name"];
    $user->lastname = $_POST["lastname"];
    $user->address = $_POST["address"];
    $user->email = $_POST["email"];
    $user->phone = $_POST["phone"];
    $user->c1_fullname = $_POST["c1_fullname"];
    $user->c1_address = $_POST["c1_address"];
    $user->c1_phone = $_POST["c1_phone"];
    $user->c1_note = $_POST["c1_note"];
    $user->user_id = $_SESSION["user_id"];
    $u = $user->add();
    $at = new AlumnTeamData();
    $at->alumn_id = $u[1];
    $at->team_id = $_POST["team_id"];
    $at->add();
    print "<script>window.location='index.php?view=team&id={$_POST['team_id']}';</script>";
}
<?php

$alumn = AlumnData::getById($_GET["id"]);
?>
<div class="row">
	<div class="col-md-12">
	<h1>Editar Alumno</h1>
	<br>
		<form class="form-horizontal" method="post" id="addcategory" action="index.php?action=updatealumn" role="form">


  <div class="form-group">
    <label for="inputEmail1" class="col-lg-2 control-label">Nombre*</label>
    <div class="col-md-6">
      <input type="text" name="name" value="<?php 
echo $alumn->name;
?>
" required class="form-control" id="name" placeholder="Nombre">
    </div>
  </div>

  <div class="form-group">
    <label for="inputEmail1" class="col-lg-2 control-label">Apellidos*</label>
    <div class="col-md-6">
      <input type="text" name="lastname" value="<?php 
echo $alumn->lastname;
?>
" required class="form-control" id="name" placeholder="Apellidos">
    </div>
  </div>
<?php

if (count($_POST) > 0) {
    $user = AlumnData::getById($_POST["alumn_id"]);
    $user->name = $_POST["name"];
    $user->lastname = $_POST["lastname"];
    $user->address = $_POST["address"];
    $user->email = $_POST["email"];
    $user->phone = $_POST["phone"];
    $user->c1_fullname = $_POST["c1_fullname"];
    $user->c1_address = $_POST["c1_address"];
    $user->c1_phone = $_POST["c1_phone"];
    $user->c1_note = $_POST["c1_note"];
    $user->user_id = $_SESSION["user_id"];
    $u = $user->update();
    Core::alert("Actualizado Exitosamente!");
    print "<script>window.location='index.php?view=team&id={$_POST['tid']}';</script>";
}