Preventing file overwriting php

Question

im creating a website where there is two textboxes. One for the file name and one for the content. When you hit submit it will create a file in a specific folder based on what you wrote. This all works well, but if you write the same file name and different content it will overwrite the file. I just want the file to be closed for writing after submitting so no one can mess with others files. Heres my php code:

    <?php
$filnavn=$_POST["filnavn"];
$innhold=$_POST["innhold"];

if($filnavn!=""){
    $myfile = fopen(dirname(__FILE__)."/lekser/".$filnavn.".txt", "w") or die("Feil! Klarer ikke å skrive filen. Prøv igjen.");
    fwrite($myfile, $innhold);
    fclose($myfile);
}
?>

Answer 1

Add a condition that checks whether or not the file already exists using file_exists() :

<?php
$filnavn = $_POST["filnavn"];
$innhold = $_POST["innhold"];
$path = dirname(__FILE__) . "/lekser/" . $filnavn . ".txt";

if ($filnavn != "" && file_exists($path))
{
    $myfile = fopen($path, "w") or die("Feil! Klarer ikke å skrive filen. Prøv igjen.");
    fwrite($myfile, $innhold);
    fclose($myfile);
}

?>

Answer 2

I'm not sure what is the expected result, so I give a totally different answer:

if you use fopen($path, "a") instead of fopen($path, "w") , you'll append the content to the existing file instead of replacing it.

Answer 3

Try this::

$filnavn = $_POST["filnavn"];
$innhold = $_POST["innhold"];
$path = dirname(__FILE__) . "/lekser/" . $filnavn . ".txt";

If file not exists then create a new file::

if ($filnavn != "" && !file_exists($path))
{
    $myfile = fopen($path, "w") or die("Feil! Klarer ikke å skrive filen. Prøv igjen.");
    fwrite($myfile, $innhold);
    fclose($myfile);
}

If file exist, append new content at bottom of existing file contents:

if ($filnavn != "" && file_exists($path))
    {
        $myfile = fopen($path, "a") or die("Feil! Klarer ikke å skrive filen. Prøv igjen.");
        fwrite($myfile, $innhold);
        fclose($myfile);
    }

If not want to make any change in existing file then create new file with adding number with file name

  if ($filnavn != "" && file_exists($path))
            {   // just add number with file name, for versioning
               $path = dirname(__FILE__) . "/lekser/" . $filnavn . "1.txt";
                $myfile = fopen($path, "w") or die("Feil! Klarer ikke å skrive filen. Prøv igjen.");
                fwrite($myfile, $innhold);
                fclose($myfile);
            }