Read file line-by-line from given byte offset. Handy for re-processing large logs files.

file-random-access.php

<?php
/**
 * Read file line-by-line from given byte offset.
 * Handy for re-processing large logs files.
 */

// Filename to use for temporary data
define('DATA_FILE', 'data.log');

// Create the data file on the fly
$data = <<<EOF
one
line two
line three
another line number four
five
six six six
seven eleven
EOF;
if (!file_put_contents(DATA_FILE, $data)) {
	print "Failed to write sample data to file\n";
	exit(1);
}

// Open file
$fh = fopen(DATA_FILE, 'r');
if (!$fh) {
	print "Failed to open file for reading\n";
	exit(1);
}

// Move to specified position, or stay on top
$from = empty($argv[1]) ? 0 : $argv[1];
fseek($fh, $from);

// Read line-by-line from given position
while (($line = fgets($fh)) !== false) {
	$line = trim($line);
	$pos = ftell($fh);
	$pos = $pos - strlen($line) - 1; // 1 is for line break
	print "Position: $pos, Line: $line\n";
}
fclose($fh);

// Remove data file
unlink(DATA_FILE);
?>