Bug fread in a txt file, read only one time - php

Question

I'm creating a code to display the name of a server with enterprise rules, So for don't use Mysql i try a new things (for me) use php to read and rewrite files, that work perfectly for one part of my code and work perfectly but for the second he only read one time, and when i do a f5 the code don't increment.
He rewrite correctly because my file was at 000 and become 001
I try to use file() but he is disable since 7.0, try to use SplFileObject but it don't want to display anything and i don't like it because i understand nothing when i use it so i come back to fopen(),fread() and fwrite() and that don't work. I'm inPHP 7.3.1
The code that works :
<?php
if ( isset($_POST) AND !empty($_POST) ) {
$nom = "./config.txt";
$filez = fopen($nom, "r") or die("Unable to open file!");
$i = fread($filez,filesize($nom));
$year = getdate();
$idy = substr($year[year], 2);
$fichier = fopen("./resultsrv.txt", "w") or die("Unable to write file!");
for ($z; $z<$_POST['nbr']+1 ; $z++) {
$id = sprintf("%04d", $i+$z);
$nome = $_POST['type'].$_POST['OS'].$idy.$id."<br>" ;
echo $nome;
$nomewout = str_replace("<br>", ";", $nome);
fwrite($fichier,$nomewout);
}
$handle = fopen("./config.txt", "w") or die("Unable to write file!");
fwrite($handle,$id);
fclose($fichier);
fclose($handle);
}
?>
and the one that doesn't work because he doesn't increment :
<?php
if ( isset($_POST) AND !empty($_POST) ) {
$fileName = 'confchass.txt';
$read = fopen($fileName,"r");
$fn = fopen($fileName,"w+");
$i = fread($read,filesize($fileName));
$id = sprintf("%03d", $i+1);
echo "<div align='center'><h1>Le Chassis</h1>";
echo $_POST['Marque'].$_POST['DC'].$id;
echo "</div>";
fwrite($fn,$id);
fclose($read);
fclose($fn);
}
?>
I want he output a thing like XXXXXX001 and when i refresh or do a new POST from my forms he output XXXXXX002 and XXXXXX003 .... But he actualy output only XXXXXX001

Answer 1

The problem is that you open the file for reading and then for writing. But from the manual...
'w+' Open for reading and writing; place the file pointer at the
beginning of the file and truncate the file to zero length. If the
file does not exist, attempt to create it.
So this will blank out the file before you read the value from it.
To fix this (using your current method, you should read the value, then open it for writing and write the new value...
$read = fopen($fileName,"r");
$i = fread($read,filesize($fileName));
fclose($read);
$id = sprintf("%03d", $i+1);
echo "<div align='center'><h1>Le Chassis</h1>";
echo $id;
echo "</div>";
$fn = fopen($fileName,"w+");
fwrite($fn,$id);
fclose($fn);
You could shorten this by using file_get_contents() and file_put_contents().