PHP Modify a single line in a text file

Question

I tried and looked for a solution, but cannot find any definitive.

Basically, I have a txt file that lists usernames and passwords. I want to be able to change the password of a certain user.

Contents of users.txt file:

user1,pass1
user2,pass2
user3,pass3

I've tried the following php code:

            // $username = look for this user (no help required)
            // $userpwd  = new password to be set 

    $myFile = "./users.txt";
    $fh = fopen($myFile,'r+');

    while(!feof($fh)) {
        $users = explode(',',fgets($fh));
        if ($users[0] == $username) {
            $users[1]=$userpwd;
            fwrite($fh,"$users[0],$users[1]");
        }
    }       

    fclose($fh);

The problem with your solution is that you are handling a text (sequential) file as a binary file. The fwrite you are using will not work here. — Hernan Velasquez, Sep 19 '12 at 05:31
your problem is an example of why you should not be using a flat text files but a data base — , Sep 19 '12 at 05:33
Also, there is the problem of synchronization. So, you should try to use [`flock`](http://php.net/manual/en/function.flock.php). Or, it could easily drive some users mad. — Prasanth, Sep 19 '12 at 06:23

score 8 · Accepted Answer · answered Sep 19 '12 at 07:57

This should works! :)

$file = "./users.txt";
$fh = fopen($file,'r+');

// string to put username and passwords
$users = '';

while(!feof($fh)) {

    $user = explode(',',fgets($fh));

    // take-off old "\r\n"
    $username = trim($user[0]);
    $password = trim($user[1]);

    // check for empty indexes
    if (!empty($username) AND !empty($password)) {
        if ($username == 'mahdi') {
            $password = 'okay';
        }

        $users .= $username . ',' . $password;
        $users .= "\r\n";
     }
}

// using file_put_contents() instead of fwrite()
file_put_contents('./users.txt', $users);

fclose($fh);

Rajat Modi · Answer 2 · 2012-12-01T09:21:41.413

I think when you get that file use file_get_contents after that use preg_replace for the particular user name

I have done this in the past some thing like here

               $str = "";

       $reorder_file = FILE_PATH;
       $filecheck = isFileExists($reorder_file);

       if($filecheck != "")
        {
            $reorder_file = $filecheck;
        }
        else
        {
            errorLog("$reorder_file :".FILE_NOT_FOUND);
            $error = true;
            $reorder_file = "";
        }
        if($reorder_file!= "")
        {
            $wishlistbuttonhtml="YOUR PASSWORD WHICH YOU WANT TO REPLACE"
            $somecontent = $wishlistbuttonhtml;
            $Handle = fopen($reorder_file, 'c+');
            $bodytag = file_get_contents($reorder_file);
            $str=$bodytag;
            $pattern = '/(YOUR_REGEX_WILL_GO_HERE_FOR_REPLACING_PWD)/i';
            $replacement = $somecontent;
            $content = preg_replace($pattern, $replacement, $str,-1, $count);
            fwrite($Handle, $content); 
            fclose($Handle);
        }

Hope this helps....

score 1 · Answer 3 · answered Sep 19 '12 at 05:54

The proper way of doing this is to use a database instead. Databases can do random access easily, doing it with text files less so.

If you can't switch to a database for whatever reason, and you don't expect to have more than about a thousand users for your system, then it would be far simpler to just read the whole file in, convert it to a PHP data structure, make the changes you need to make, convert it back into text and overwrite the original file.

In this case, that would mean file() to load the text file into an array with each element being a username and password as a string, explode all elements on the array at the comma to get the username and password separately, make the changes you need to make, then write the modified data to disc.

You might also find fgetcsv() useful for reading the data. If you SplFileObject and have a recent version of PHP then fputcsv() may also be available to write the data back out.

However, just using a database is a far better solution. Right tool for the job.

score 1 · Answer 4 · edited May 01 '20 at 09:33

$fn = fopen("test.txt","r") or die("fail to open file");

$fp = fopen('output.txt', 'w') or die('fail to open output file');
while($row = fgets($fn)) 
{
    $num    = explode("++", $row);

    $name   = $num[1];
    $sex    = $num[2];
    $blood  =  $num[3];
    $city   = $num[4];

    fwrite($fp, "Name:  $name\n");
    fwrite($fp, "Sex:   $sex\n");
    fwrite($fp, "Blood: $blood\n");
    fwrite($fp, "City:  $city\n");
}
fclose($fn);
fclose($fp);

score 0 · Answer 5 · answered Sep 19 '12 at 07:23

If you're on a *nix system you could use sed; I find it neater than playing with file handles etc:

exec("sed -i '/^$username,.\+\$/$username,$userpwd/g' ./users.txt 2>&1", $output, $return);

If not I'd agree with GordonM and parse the file into a PHP data structure, manipulate it, then put it back:

$data = file_get_contents('./users.txt');

$users = array_map(function($line) {
  return explode(',', $line);
}, explode("\n", $data));

foreach ( $users as $i => $user ) {
  if ( $user[0] == $username ) {
    $user[1] = $userpwd;
    $users[$i] = $user;
  }
}

file_put_contents('./users.txt', implode("\n", array_map(function($line) {
  return implode(',', $line);
}, $users)));

There are, of course, an infinite number of ways of doing that!

PHP Modify a single line in a text file

5 Answers5

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