<?php

$REQUEST['nome'] = 'joao';
$REQUEST["ra"] = 'teste';
$REQUEST["gender"] = 'teste';
$REQUEST["idade"] = 'teste';
$REQUEST["endereco"] = 'teste';
$REQUEST["telefone"] = 'teste';
$REQUEST["email"] = 'teste';

session_start();
$_SESSION['cadastro'] = [];
$cads = count($_SESSION['cadastro']);

if($cads == 0){
	$_SESSION['cadastro'][0] = $REQUEST;
}else{
	$new_cad = $cads + 1;
	$_SESSION['cadastro'][$new_cad] = $REQUEST;
}

print_r($_SESSION);