PHP - Stop while loop after reading every single line from text file - php

Question

I want the Code below to read individual line of text from dataFile.txt and show it in input field.
Problem is After reading first line from text document it shows all remaining lines of text from text file into input field. But on clicking submit it should show second line only then again on submitting it should show third line only, inside input field. please help.
<?php
$file = __DIR__."/dataFile.txt";
$f = fopen($file, "r");
$array1 = array();
<form action="datagGet.php" method="get">
<input type="text" value="
<?php while ( $line = fgets($f, 100) )
{
$nl = mb_strtolower($line);
echo $nl;
if(isset($_GET['done']))
{
$nl++;
}
else
{
break;
}
}
?>"
name="someText">
<input type="submit" name="done" >
</form>

Answer 1

You have several problems with you code. And the first comment above points to many of the. Key is the fact that the $_GET['done'] is set for the form submit and therefore you will echo all the lines of the output. It never breaks.
Also there is the fact that you are opening the file for reading each submit of the form. Although I don't see a simple way around this unless you store the file contents between requests.
One possible option is to use 'file()' to read the entire contents into an array. And then use sessions to store which line has been read. Then on each submit, look for the index of the array from the session read; advance it by one read the file again and return that line. Wow wasteful. But okay for simple site.
so use file to get the lines in an array.
output the first line into the value.
store the next index to be read in the $_SESSION variable like $_SESSION['next_line'] = 1
then upon further submissions. read it all back in. look up the 'next_line', and output that line.
so, for example
$array = file('your file name');
$output = $array[0];
if (isset($_SESSION['next_line']))
$_SESSION['next_line'] = intval($_SESSION['next_line']) + 1;
else
$_SESSION['next_line'] = 1;//prime the pump
echo the form with $output
then rinse and repeat. e.g. read, get output (next_line) with file, set $_session = next_line + 1; render output in form.
ps. some extra notes
* of course you'll need to start session on each request.
* you'll need to check if the $_SESSION['next_line'] is set. if not, set it to 1 (prime it)