Invalid argument supplied for foreach() + Logic of Script - php

Question

I posted a similar question earlier today, however I recently downloaded xampp and can now get syntax errors. I'm very new to all of this.
Please see this example to see the current state of my .php file: http://rich2233.comoj.com/file2.php
I can get the .txt file to extract and display the content from the .txt file, but any attempt of modifying the .txt file does not happen.
When I ran this on xampp, I got this error: Invalid argument supplied for foreach() in file2.php on line 30

Answer 1

After your most recent update of the code: The answer to the error message in the question title is:
The code is missing the line $users = file("test.txt");

Answer 2

Here's a quick tip: keep track of your iterator. Confusing? Think of each row number as unique offset in the file. You need to iterate (foreach) and increment it by +1 each time. When you're editing a row later on, you just need to submit the offset number, iterate again and check if $i == $_POST['iterator'].
// Iterator example
$users = file('text.txt');
$hours_taken = array();
foreach ($users as $user) {
list($time, $name) = explode('|', $user);
array_push($hours_taken, $time);
}
// Assuming same order of rows in users.txt
$hours = array('8:00 am', '9:00 am', '10:00 am'); // ...5:00 pm
$i = 1;
echo '<select name="time"><option selected>-- Select time --</option>';
foreach ($hours as $hour) {
if (in_array($hour, $hours_taken)) {
echo '<option disabled=disabled>'. $hour .'</option>';
}
else {
echo '<option value='. $i .'>'. $hour .'</option>';
}
$i++;
}

Answer 3

Edited as that last function wouldn't have worked
function editTxt(){
$find_name = $_POST['name'];
$find_time = $_POST['time'];
$filename = getcwd() . "/test.txt";
$lines = file( $filename , FILE_IGNORE_NEW_LINES );
foreach($lines as $key => $line)
{
list($time, $name) = explode('|', $line);
if($time == $find_time && $name == "Available")
{
$lines[$key] = $time."|".$find_name;
file_put_contents( $filename , $lines );
break;
}
}
}
If you are planning to use this for something other than just an exercise I suggest using a database.

Answer 4

Try:
$users = file($filename);
I suspect $users === false as you aren't using the same "calculated" file name.