PHP Grab last 15 lines in txt file - php

Question

Thank you for taking the time to read this and I will appreciate every single response no mater the quality of content. :)
Using PHP, I'm trying to get the last 15 lines of a text document (.txt) and store that data into a php variable. I understand that this is possible, however when I do get the last 15 lines, is it possible to retain the order? For example:
text document:
A
B
C
When I grab the text document from the last 15 characters, I don't want the echo to end up like:
C
B
A
All assistance is appreciated and I look forward to your replies; thank you. :) If I didn't explain anything clearly and/or you'd like me to explain in more detail, please reply. :)
Thank you.

Answer 1

Try using array_slice, which will return a part of an array. In this case you want it to return the last 15 lines of the array, so:
$filearray = file("filename");
$lastfifteenlines = array_slice($filearray,-15);

Answer 2

If you don't mind loading the entire file into memory:
$lines = array_slice(file('test.txt'), -15);
print_r($lines );
If the file is too large to fit into memory you can use a circular method:
// Read the last $num lines from stream $fp
function read_last_lines($fp, $num)
{
$idx = 0;
$lines = array();
while(($line = fgets($fp)))
{
$lines[$idx] = $line;
$idx = ($idx + 1) % $num;
}
$p1 = array_slice($lines, $idx);
$p2 = array_slice($lines, 0, $idx);
$ordered_lines = array_merge($p1, $p2);
return $ordered_lines;
}
// Open the file and read the last 15 lines
$fp = fopen('test.txt', 'r');
$lines = read_last_lines($fp, 15);
fclose($fp);
// Output array
print_r($lines);
This method will also work if the file has less than 15 lines- returning an array with however many lines are in the file.

Answer 3

You can use fseek with a negative position to seek backwards through the file, counting newlines as you go.
I'm too tired to write up copy/past-able code, but there are some examples in the comments to the manual page for fseek that are very close to what you want.

Answer 4

If the file isn't bigger than available memory you can do this:
$fArray = file("filename");
$len = sizeof($fArray);
for($i=$len -15;$i<$len ;$i++)
{
echo $fArray[$i];
}
If you have a file that is hundreds of megabytes :
$rc = fopen("file","r");
for ($i=0; $line = fgets($file) ;$i++)
{
if ($i%15 == 0)
{
$last15 = array();
}
$last15[] = $line;
}
echo join("\n",$last15);

Answer 5

the longer array solution:
array_slice(explode("\n",file_get_contents($file)),-15);
the shorter array solution:
array_slice(file($file),-15);

Answer 6

This code will open the file, show the total lines, show the header of file and show the last lines of file defined in $limit.
<?php
// open the file in read mode
$file = new SplFileObject('file.csv', 'r');
// get the total lines
$file->seek(PHP_INT_MAX);
$last_line = $file->key();
echo $last_line;
echo "<br>";
// Rewind to first line to get header
$file->rewind();
// Output first line if you need use the header to make something
echo $file->current();
echo "<br>";
// selecting the limit
$limit = 6;
// selecting the last lines using the $limit
$lines = new LimitIterator($file, $last_line - $limit, $last_line);
//print all the last 6 lines array
//print_r(iterator_to_array($lines));
//echo "<br>";
// Loop over whole file to use a single line
foreach ($lines as $line) {
print_r($line);
echo "<br>";
}