tail.php

<?php

/**
 * A script to emulate the UNIX tail function by displaying the last X number
 * of lines in a file.
 *
 * Useful for large files, such as logs, when you want to process lines in PHP
 * or write lines to a database.
 *
 * @author Dan Ruscoe
 */

// The name of the file to read
define('FILE_NAME','file.log');

// The number of lines to display
define('LINES_TO_DISPLAY',10);

if (!is_file(FILE_NAME)) {
	die("Not a file - ".FILE_NAME."\n");
}

if (LINES_TO_DISPLAY < 1) {
	die("Number of lines to display must be greater than 0\n");
}

if (!$lines = get_lines(FILE_NAME,LINES_TO_DISPLAY)) {
	die("Could not get lines from file - ".FILE_NAME."\n");
}

foreach ($lines as $line) {
	echo $line;
}

exit;

/**
 * Returns an array containing X number of rows from the end of a file.
 *
 * @param string $filename
 * @param int $lines_to_display
 * @return array
*/

function get_lines($filename,$lines_to_display) {

	// Open the file.
	if (!$open_file = fopen($filename,'r')) {
		return false;
	}

	$pointer = -2;	// Ignore new line characters at the end of the file

	$char = '';

	$beginning_of_file = false;

	$lines = array();

	for ($i=1;$i<=$lines_to_display;$i++) {

		if ($beginning_of_file == true) {
			continue;
		}

		/**
		 * Starting at the end of the file, move the pointer back one
		 * character at a time until it lands on a new line sequence.
		 */

		while ($char != "\n") {

			// If the beginning of the file is passed
			if(fseek($open_file,$pointer,SEEK_END) < 0) {

				$beginning_of_file = true;

				// Move the pointer to the first character
				rewind($open_file);

				break;

			}

			// Subtract one character from the pointer position
			$pointer--;

			// Move the pointer relative to the end of the file
			fseek($open_file,$pointer,SEEK_END);

			// Get the current character at the pointer
			$char = fgetc($open_file);

		}

		array_push($lines,fgets($open_file));

		// Reset the character.
		$char = '';

	}

	// Close the file.
	fclose($open_file);

	/**
	 * Return the array of lines reversed, so they appear in the same
	 * order they appear in the file.
	*/

	return array_reverse($lines);

}

?>