在 php 中向多维数组中插入新元素

Question

<?php
  $accounts = [["felh" => "minta", "password" => "Meow123", "mail" => "pelda@gmail.com"],
  ["felh" => "minta2", "password" => "Meow1232", "mail" => "pelda2@gmail.com"]];
 if (isset($_POST["regisztral"])) {
    $username = $_POST["felh"];
    $password = $_POST["password"];
    $email = $_POST["mail"];
    $password2 = $_POST["password2"];
       if (strlen($password) < 8)
       die("<b>error<b>");
       if ($password !== $password2)
       die("<b>error</b>");
        if ($_POST['feltetel'] != 'igen') die("<b>error</b>");
        foreach ($accounts as $account) {
        if ($account["felh"] === $username)     die("<b>error:</b> taken!");
         if ($account["mail"] === $email)     die("<b>error:</b>taken!");
        }

            $accounts[] = ["felh" => $username, "password" => $password, "mail" => $email];
        $file = fopen("accounts.txt", "w");
             foreach ($accounts as $account)
             fwrite($file, serialize($account) . "\n");
             fclose($file);

     echo "<br>Succeed<br/>";
     }

The user has to fill in a registration form and my program should decide whether his username and email adress are taken or not. I want to sort all usernames, passwords and email adresses into a 2 dimensional array and then write it into a text file. My problem is that every time I insert a new record into the array, it switches the last element to the one I just inserted instead of keeping it and adding the new element to the end of the array. How could I solve it?

*edit I uploaded the entire php section of my code. So to be clear, my problem is the following: the 2 records I added manually at the beginning of the code work perfectly. When I want to insert let's say cat aaaaaaaa and nothing@gmail.com it Works perfectly. But when I submit another value after that, let's say dog bbbbbbbb and something@gmail.com it switches cat aaaaaaaaa and nothing@gmail.com to dog bbbbbbbb and something@gmail.com. What I want however is keeping cat aaaaaaaa nothing@gmail.com and THEN adding dog bbbbbbbb something@gmail.com to the end of the array

Answer 1

What is causing problem for you is php function fopen() and mode. Currently in code you use mode 'w' and by php manual that mode is:

Open for writing only; place the file pointer at the beginning of the file and truncate the file to zero length. If the file does not exist, attempt to create it.

Everytime you overwrite this file named accounts.txt with new data.

So you should use mode 'a' to place pointer at the end of file and append new data.

Open for writing only; place the file pointer at the end of the file. If the file does not exist, attempt to create it. In this mode, fseek() has no effect, writes are always appended.

test: https://repl.it/@kallefrombosnia/DiscreteOnerlookedLists