PHP: File writing issue - php

Question

I'm trying to make a function that writes a list of scores for players.
For example:
player_1 100 12 12 10
player_2 39 13 48 29
And when players beat (or do worse) than their previous scores, their score is over-written with the new score.
I've written a function that sort of works, but has multiple problems.
function write($player)
{
global $logfile;
$lines = file($logfile);
foreach($lines as $i => $line)
{
$pieces = explode(" ", $line);
$pieces[0] = trim($pieces[0]);
if( $pieces[0] == $player->name ) //found name
{
trim($lines[$i]);
unset($lines[$i]); //remove the old player data
$lines[$i] = "{$player->name} {$player->lvl} {$player->exp} {$player->mana} \n"; //write the new score
$fp = fopen($logfile,'a');
fwrite($fp,$lines[$i]);
$found = TRUE;
break;
}
}
if(!$found) //record a new player whose score isn't in the file
{
$fp = fopen($logfile,'a');
$newp = "$player->name $player->lvl $player->exp $player->mana \n";
fwrite($fp, $newp);
}
fclose($fp);
}
The file just appends the new score and doesn't overwrite the previous score. Could someone point out my errors?

Answer 1

Try changing:
$fp = fopen($logfile,'w');
into
$fp = fopen($logfile,'a');
in your
if( $pieces[0] == $player->name ) ...
PHP.fopen file open modes ;)
EDIT
You can override your player entry by putting the fwrite() after foreach loop by overriding the whole file with joined lines (this may cause performace issues).
Or
Try to loop line by line using fgets() and then if you will find the right match use fseek() to the previous line and override it ;)
fgets() fseek()
SECOND EDIT
<?php
$find = 'player_1';
$h = fopen('play.txt','r+');
$prev_pos = 0;
while(($line = fgets($h, 4096)) !== false){
$parts = explode(' ', $line);
if($parts[0] == $find) {
fseek($h, $prev_pos);
fwrite($h, "player_222 12 22 411");
break;
}
$prev_pos = ftell($h);
}
fclose($h);
?>
Code sample as requested ;) The idea is to save previous line position and then use it to fseek and override. I'm not sure if the fwrite will work well on all enviroments without PHP_EOL at the end-of-line, but on mine it's fine.

Answer 2

First, let us see the reason why it duplicates the record. $lines is an array in which you are updating the record of the specific player. But after updating the record, you are appending it to the file (using "a" mode) and therefore duplicating the entry of that player.
The idea should be to update that record in the file. And with your logic, the best thing is to rewrite $lines to the file. Since $lines will always contain the updated entry, it makes sense.
Now coming to the logic where you are making an entry for a new player. There is nothing wrong in that logic but it could be improved by appending the new entry to $lines instead of writing to the file.
Here is the updated code. Please note that I've removed lines that weren't needed.
function write($player) {
global $logfile;
$found = FALSE;
$lines = file($logfile);
foreach($lines as $i => $line) {
$pieces = explode(" ", $line);
$pieces[0] = trim($pieces[0]);
if( $pieces[0] == $player->name ) { //found name
$lines[$i] = "{$player->name} {$player->lvl} {$player->exp} {$player->mana} \n"; //write the new score
$found = TRUE;
break;
}
}
if(!$found) { //record a new player whose score isn't in the file
$lines[] = "$player->name $player->lvl $player->exp $player->mana \n";
}
file_put_contents($logfile, $lines);
}
Hope it helps!

Answer 3

Is this code run on a web server with many users accessing at the same time?
If it is, imagine what happens when one user has just opened the file for writing, the file is emptied, and another opens it for reading before the first one has finished writing the data.
A partial solution is write to a temp file and rename the temp as the original when you are done. Rename is atomic, so the users will see either the original file or the new one and not something in between.
But youll still miss some updates. You could lock the file, meaning that when one person is writing another can't read. To do that you would use the flock function: http://php.net/manual/en/function.flock.php
The proper solution is using a real database. Sqlite for example is nice and simple: no external server processes or passwords...