How to read specific line text with interval using PHP - php

Question

i want read line in text file, with interval 4 , 4 lines show per page..
if load domain.com/pages/page2.php
output read line (5,6,7,8)
if load domain.com/pages/page3.php
output read line (9,10,11,12)
my code
$file1 = basename($_SERVER["SCRIPT_FILENAME"], '.php') ;
$file1 = preg_replace("/.+?(\\d+).*/", "$1", $file1);
$file2 = ($file1 - 1);
$file3 = ($file2 *4);
$file4 = ($file3 + 3 );
function retrieveText($file, $init, $end, $sulfix = '')
{
$i = 1;
$output = '';
$handle = fopen($file, 'r');
while (false === feof($handle) && $i <= $end) {
$data = fgets($handle);
if ($i >= $init) {
$output .= $data . $sulfix;
}
$i++;
}
fclose($handle);
return $output;
}
echo retrieveText('file.txt', $file3, $file4, '<br>');
not work, missing lines

Answer 1

First of all, I'm gonna advise you to get rid of your REGEX name getter and just have the following format:
domain.com/pages?page=1
domain.com/pages?page=2
domain.com/pages?page=3
So on and so forth. You will be using $_GET['page'] to retrieve the page number.
Now, the way that I'd go with it is to have an array with all the lines of the text and to use the array_slice() function. Something along this should do:
function retrieveText($file, $page, $per_page, $suffix)
{
$content = file_get_contents($file);
$array = explode(PHP_EOL, $content);
$start = --$page * $per_page;
$lines = array_slice($array, $start, $per_page);
$output = '';
foreach ($lines as $line) {
$output .= $line . $suffix;
}
return $output;
}
You should then call this function like this:
$page = $_GET['page'];
$page = $page === null ? 1 : $page;
retrieveText('file.txt', $page, 4, '<br>');