如何使用ajax和php创建和更新文本文件？

Question

When I call my PHP file directly, it makes a text file exactly as I expected. But when I use AJAX, it doesn't make the text file.

I gave pemissions to directory and files: chmod(0777) and setup allow_url_fopen as "ON".
I made sure the AJAX is calling indexing.php, but no text files are created.

What's going wrong?

$('#btn_index').on('click', function(){
  $.ajax({url: "/indexing.php", success: function(result){
    alert("Indexing is finished");
  }});
});

indexing.php

<?php

$fWrite = fopen(__DIR__."/indexOfFiles.txt","w+") or die('Cannot open file:  ');

if ($handle = opendir('./data/pdffiles')) {

    while (false !== ($entry = readdir($handle))) {

        if ($entry != "." && $entry != "..") {


            $wrote = fwrite($fWrite, "$entry".PHP_EOL);
        }
    }
}


closedir($handle);
fclose($fWrite);

$fWrite = fopen(__DIR__."/arrays.txt","w+") or die('Cannot open file:  ');
$wrote = fwrite($fWrite, '{"data": []}');

fclose($fWrite);
?>