php - one time access by looking up serial in a .dat file - php

Question

i've now written this short script.
It records a serial or token number, checks to see if its in a .dat file, and allows access if its present. Otherwise it denies access to the site.
It also removes the token from the file once it has been redeemed as it were.
However, when i add multiple tokes in the dat file, the code doesn work properly. It only works with a single entry. How would i make it work for multiple entries.
im thinking of maybe implementing some sort of array somewhere? or explode?
index.php
require_once "married.php";
session_start();
$url_request = (isset($_SERVER['HTTPS']) ? "https" : "http") .
"://$_SERVER[HTTP_HOST]$_SERVER[REQUEST_URI]";
$ip = $_SERVER['REMOTE_ADDR'];
$token = substr($url_request,45);
$_SESSION["cookie"] = $token;
$tk = $_SESSION["cookie"];
$ips = array();
$page = file("urls.dat");
foreach($page as $line)
{
array_push($ips, $line);
}
if(in_array($tk, $ips))
{
//header("Location: mysite.co.uk");
echo "<title>My Site</title>Here is my site";
$file = fopen("ip_match.dat","a");
fwrite($file,$tk . " " . $ip . "\r\n");
fclose($file);
$oldMessage = $_SESSION["cookie"];
$deletedFormat = "";
$str=file_get_contents('urls.dat');
$str=str_replace("$oldMessage", "$deletedFormat",$str);
file_put_contents('urls.dat', $str);
exit;
} else {
echo ("<title>404 Not Found</title>
<h1>Not Found</h1>The requested URL was not found on this server.
<br>
<br>
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request. test");
exit;
}
urls.dat
1089yht
url: http://mmmmmmmmmmmmm.co.uk/url/index.php?key=1089yht
ps. Happy Holidays all!

Answer 1

Look at JSON. You could do something like this:
$tokens = ['foo', 'bar'];
file_put_contents('urls.json', json_encode($tokens));
// and then you can decode it back
// returns ['foo', 'bar']
$decodedTokens = json_decode(file_get_contents('urls.json'));
If you still want to use simple text file, you could save every record at new line and then load line by line.
$tokens = [];
while(! feof($file)) {
$line = fgets($file);
// or save to array
$tokens[] = $line;
}
fclose($file);

Answer 2

try
$str = preg_replace("/{$oldMessage}/", $deletedFormat, $str, 1);
Instead of
$str=str_replace("$oldMessage", "$deletedFormat",$str);
Because: str_replace replaces everything.
preg_replace lets you limit how many replacements.