Reading & Writing Files

<?php
declare(strict_types=1);

// ── Simple reads ──────────────────────────────────────────────
// file_get_contents - reads entire file into string (up to ~50MB safely)
$content = file_get_contents("/var/www/html/storage/posts/php-basics.md");
if ($content === false) {
    throw new RuntimeException("Could not read file.");
}

// file - reads into array of lines (each line is an element)
$lines = file("/path/to/data.txt", FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);

// Read only N bytes (header sniffing, configuration snippets)
$handle = fopen("/path/to/large.log", "rb");
if ($handle === false) throw new RuntimeException("Cannot open log file.");
$firstLine = fgets($handle);   // read one line
fclose($handle);

// ── Simple writes ─────────────────────────────────────────────
// file_put_contents - optimal for full overwrites
$bytesWritten = file_put_contents(
    "/var/www/html/storage/cache/homepage.html",
    $renderedHtml,
    LOCK_EX   // lock file during write - prevents concurrent corruption
);

// Append to an existing file
file_put_contents(
    "/var/www/html/storage/logs/app.log",
    date("[Y-m-d H:i:s] ") . "Post published: php-basics
",
    FILE_APPEND | LOCK_EX
);

// ── fopen - fine-grained control (large files, line-by-line) ──
$source      = fopen("/storage/exports/posts.csv", "rb") ?: throw new RuntimeException("Cannot open.");
$destination = fopen("/storage/exports/posts_backup.csv", "wb") ?: throw new RuntimeException("Cannot create.");

// Copy in 8KB chunks - never loads full file into RAM
while (!feof($source)) {
    $chunk = fread($source, 8192);
    fwrite($destination, $chunk);
}
fclose($source);
fclose($destination);

// ── Directory operations ──────────────────────────────────────
// Create directory (with parents) if not exists
$uploadDir = "/var/www/html/storage/uploads/" . date("Y/m");
if (!is_dir($uploadDir)) {
    mkdir($uploadDir, 0755, true);   // recursive
}

// List directory contents
$iterator = new DirectoryIterator("/var/www/html/storage/logs");
foreach ($iterator as $file) {
    if ($file->isDot() || !$file->isFile()) continue;
    echo $file->getFilename() . " - " . $file->getSize() . " bytes
";
}

// ── SplFileInfo - OOP file info ───────────────────────────────
$info = new SplFileInfo("/var/www/html/public/index.php");
echo $info->getFilename();    // "index.php"
echo $info->getExtension();   // "php"
echo $info->getSize();        // bytes
echo $info->getMTime();       // last modified Unix timestamp
echo $info->getPathname();    // full path

// ── Temporary files ───────────────────────────────────────────
$tmpFile = tempnam(sys_get_temp_dir(), "blog_");
file_put_contents($tmpFile, $processedData);
// ... process ...
unlink($tmpFile);  // always clean up!