File Handling

PHP streams unify files and other sources. Modes control reading, append, truncation, creation, and binary semantics. Every failure and partial write must be handled.

Practical example

<?php
$handle = fopen($path, 'xb');
if ($handle === false) throw new RuntimeException('open failed');
try { if (!flock($handle, LOCK_EX) || fwrite($handle, $data) === false) throw new RuntimeException('write failed'); }
finally { fclose($handle); }

Never concatenate raw user paths into privileged roots. Constrain resolved paths, permissions, sizes, and symlink behavior. Stream large data. Important replacement often writes a temporary sibling and renames it atomically where supported.