session_start() error: why it doesn´t recognize a new session? - php

Question

I´m testing a php exercise, and I can´t get it working properly. It´s a counter that stores the visits inside a txt file as a simple integer. Every time I reload the page the number gets a +1.
Now, I want it to reload only when there´s a new visit, so I´m trying sesion_start() for the first time.
In class, this example worked just fine, but when I try to reproduce it at home, the number won´t change, even if I close the browser and open it again.
This is my code (it´s inside the php tags, naturally):
session_start();
if (!$_SESSION[contador]) {
define('ARCHIVO', 'visitas.txt');
if (file_exists(ARCHIVO)) {
$fp=fopen(ARCHIVO, 'r');
$cant=fread($fp,filesize(ARCHIVO));
fclose($fp);
} else {
$cant=0;
}
$cant++;
$fp=fopen(ARCHIVO, 'w');
fwrite($fp, $cant);
fclose($fp);
$_SESSION[contador]=$cant;
}
echo '<h3>Hay '.$_SESSION[contador].' visitas.</h3>';

Answer 1

contador should be in quotes unless it's a defined constant somewhere?? I assume it's a string
$_SESSION["contador"]
Try this out. It's different, but it'll do something at least. Would've posted as a comment, but I wanted code formatting.
session_start();
if(empty($_SESSION['contador'])){
$_SESSION['contador']=1;
}else{
$_SESSION['contador']++;
}
echo '<h3>Hay '.$_SESSION['contador'].' visitas.</h3>';

Answer 2

First of all, #Lenny is correct. $_SESSION['contador'] is what is called a session variable or a variable assigned to the $_SESSION array. So it MUST BE in quotes. That is not optional. And you cannot define a constant and use that value inside the brackets.
if you had a constant, you could set the session variable to that. But, since your value is variable, as you are adding incrementally, it is by definition not constant.
Furthermore, refreshing your Web browser will keep your session active. So if you truly want to test this, try session_destroy(); at some point.
Here is how this code will work (the storage of the session variable anyway):
<?php
session_start();
if(!isset($_SESSION['contador'])) {
define('ARCHIVO', 'visitas.txt');
if(file_exists(ARCHIVO)) {
$fp = fopen(ARCHIVO, 'r');
$cant = fread($fp,filesize(ARCHIVO));
fclose($fp);
} else {
$cant=0;
}
$cant++;
$fp = fopen(ARCHIVO, 'w');
fwrite($fp, $cant);
fclose($fp);
$_SESSION['contador'] = $cant;
}
echo '<h3>Hay ' . $_SESSION['contador'] . ' visitas.</h3>';
?>
Note: your logic is bad. Your are telling your script that $cant is either equal to the value of the txt file OR it is equal to 0. Then your are incrementing that value by one. You will perform that task on each load. You need to modify this code and finish your conditional statement.
<?php
session_start();
if(!isset($_SESSION['contador'])) {
define('ARCHIVO', 'visitas.txt');
if(file_exists(ARCHIVO)) {
$fp = fopen(ARCHIVO, 'r');
$cant = fread($fp,filesize(ARCHIVO));
fclose($fp);
} else {
$cant=0;
}
$cant++;
$fp = fopen(ARCHIVO, 'w');
fwrite($fp, $cant);
fclose($fp);
$_SESSION['contador'] = $cant;
} else {
$_SESSION['contador']++;
}
echo '<h3>Hay ' . $_SESSION['contador'] . ' visitas.</h3>';
?>
I hope this helps.