PHP readfile() Function: Description, Parameters, Return Value, and Example

The PHP readfile() function reads a file and writes it to the output buffer, returning the number of bytes read or FALSE on error.

Signature:

int readfile(string $filename[, bool $use_include_path = false[, resource $context]])

Parameters:

filename : the name of the file to read.

use_include_path : optional boolean to search in include_path.

context : stream context resource.

Return value: Number of bytes read, or FALSE on failure (error message shown unless suppressed with @readfile()).

Example:

<?php
$file = 'monkey.gif';
if (file_exists($file)) {
    header('Content-Description: File Transfer');
    header('Content-Type: application/octet-stream');
    header('Content-Disposition: attachment; filename="' . basename($file) . '"');
    header('Expires: 0');
    header('Cache-Control: must-revalidate');
    header('Pragma: public');
    header('Content-Length: ' . filesize($file));
    readfile($file);
    exit;
}
?>

Tips: readfile() itself does not cause memory problems; if memory exhaustion occurs, ensure output buffering is disabled using ob_get_level().