How to insert data from a form into a table in php without using databsaes?

I need to create a table of 17 rows where each row contains information such as row number, name, surname, email and birthday. The data is provided by this form:

<form action="index.php" method="post">
      <input type="text" name="name" placeholder="name" />
      <input type="text" name="surname" placeholder="surname" />
      <input type="text" name="emailbirthday" placeholder="emailbirthday" />
      <input type="text" name="birthday" placeholder="birthday(dd/mm/aaa)" />
      <button type="reset">Reset Form</button>
      <button type="submit">Submit Form</button>
    </form>

After clicking submit the data should be displayed in the nth row of the table(row number one if it is the first "pack" of data submitted, number two if its the second and so on). This problem could easely be solved using databases but i cannot use them(by professors order).

I tried to create an array than push values into it like this:

$array_name = array();

$name = $_POST["name"];

array_push($array_name, $name);

This approach doesn't work(the index of the array stays 0 alla of the time so it keeps replacing the first value again and again) and manually incrementing the index counter of the array doesn't work either.

Solution

Normally one should use a database approach but your professor explicitly forbids it.

There are many other ways to do it. (store as TEXT/JSON/CSV file or localstorage / cookies), etc. For me I would use session to do the job

declare a session variable which is an array
if user submits the form, store the POST data into another array (subarray) containing name, surname, birthday, email
add the subarray into the main session variable array
print it out at the end as a table

So the PHP will be:

<?php
session_start();
?>
<form action="#" method="post">
      <input type="text" name="name" placeholder="name" />
      <input type="text" name="surname" placeholder="surname" />
      <input type="text" name="email" placeholder="email" />
      <input type="text" name="birthday" placeholder="birthday(dd/mm/aaa)" />
      <button type="reset">Reset Form</button>
      <button type="submit">Submit Form</button>
</form>

<?php

if (!isset($_SESSION["arr"])){
  $_SESSION["arr"]=array();
}

if ($_POST) {
   $subarray=array(
       "name"=>$_POST["name"], 
       "surname"=>$_POST["surname"],
       "birthday"=>$_POST["birthday"],  
       "email"=>$_POST["email"]
   );
 $_SESSION["arr"][]=$subarray;
}

echo "<table border=1><tr><td>Name<td>Surname<td>Email<td>Birthday";

foreach($_SESSION["arr"] as $suba){
   echo "<tr><td>" . $suba["name"]  ;
   echo "<td>" . $suba["surname"] ;
   echo "<td>" . $suba["email"]  ;
   echo "<td>" . $suba["birthday"]  ;
}
echo "</table>";
?>

However, if you need the data to be persistent (even after the user closes the browser), then you need to store the data say in file format or cookies, etc.