How to use a text file to log users in - php

Question

I have tried and tried to get this to work. Essentially I want to read a line of a text file and compare it to the user input. If they are the same then it will continue the log in process.
For now I am just using an echo to see if it actually finds something. it seems that the if statement doesn't see the two inputs as a match even when they are.
$myFile = fopen("users.txt", "r");
$username = $_POST['username'];
while(!feof($myFile))
{
$userN = fgets($myFile);
//compares entered user to text file users
if (($username === $userN)){
echo 'found';
}
}
The only time that it ever finds a match is if the input is left blank as it will be matched with the final line of the file.

Answer 1

Try this code.
<?php
$myFile = fopen("users.txt", "r");
$username = $_POST['username'];
while(!feof($myFile))
{
$userN = fgets($myFile);
//$userN = rtrim(fgets($myFile, "\r\n")); //More cleaner way suggested in comment
//compares entered user to text file users
if ($username == trim($userN)){
echo 'found';
} else {
echo "non found";
}
}
I guess $userN is taking some white spaces or other predefined characters before or after string, so use trim() to remove it.

Answer 2

Although it's not the best way to check users exist, you can load all the users using file() (without the new line and removing any blank entries), which will produce an array of the users. Then just use in_array() to see if the user is in the list...
$username = $_POST['username'];
$userList = file("users.txt", FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
if ( in_array($username, $userList)) {
echo "Found";
}

Answer 3

how are you store user information? are you using commas or something else to separate users and can't you use JSON instead of this in that way it's much easier to store, retrieve and check. if you still need to use i wold like to suggest this method first get all and store in string then convert it to array using PHP function explode and then check the array (assuming text file only contain user name and user separate by , )
myuser.txt
jhone,jonney,mark kevin
read.php
$file = file_get_contents('./myuser.txt', FILE_USE_INCLUDE_PATH);
$arry = explode(",",$file);
$count = 0;
while($count<sizeof($arry)){
if($arry[$count]== $userInput){
echo 'found';
}else{
echo "non found";
}
$count++;
}