Common PHP Code Snippets for File Operations, Database Singleton, URL Handling, and Miscellaneous Utilities

This article provides a set of useful PHP code examples for everyday development tasks.

1. Traverse all files and directories

function fileShow($dir) {
    $handle = opendir($dir);
    while ($file = readdir($handle)) {
        if ($file !== '..' && $file !== '.') {
            $f = $dir . '/' . $file;
            if (is_file($f)) {
                echo '|--' . $file . '<br>';
            } else {
                echo '--' . $file . '<br>';
                fileShow($f);
            }
        }
    }
}

2. MySQLi singleton pattern

class db {
    private $con;
    private static $instance;
    private function __construct($host, $username, $password, $database) {
        $this->con = mysqli_connect($host, $username, $password);
        if (!$this->con) die("连接失败！");
        mysqli_select_db($database);
    }
    public static function getInstance($host, $username, $password, $database) {
        if (self::$instance) return self::$instance;
        self::$instance = new db($host, $username, $password, $database);
    }
    public function close() {
        return mysqli_close($this->con);
    }
    private function __clone() {}
}

3. Get content of a web page

$url = "http://www.phpres.com/index.html";
$str = file_get_contents($url);
// or using cURL
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_exec($ch);
curl_close($ch);

4. Extract file extension from a URL

function getExt1() {
    $url_path = "http://www.sina.com.cn/abc/de/fg.php?id=1";
    $temp = pathinfo($url_path, PATHINFO_EXTENSION);
    $temp = explode("?", $temp);
    echo $temp[0]; // php
}
function getExt2() {
    $url_path = "http://www.sina.com.cn/abc/de/fg.php?id=1";
    $temp = parse_url($url_path);
    echo pathinfo($temp['path'], PATHINFO_EXTENSION);
}

5. Get a file's extension

function get_ext1($file_name) { return strrchr($file_name, '.'); }
function get_ext2($file_name) { return substr($file_name, strrpos($file_name, '.')); }
function get_ext3($file_name) { $tmp = explode('.', $file_name); return array_pop($tmp); }
function get_ext4($file_name) { return pathinfo($file_name, PATHINFO_EXTENSION); }

6. Convert snake_case to Camel Case

function conversion1() {
    $str = "open_door";
    return ucwords(str_replace('_', ' ', $str)); // Open Door
}

7. Header redirects

header('location:index.php'); // redirect
header('HTTP/1.1 404 Not Found'); // send 404 status

8. Remove all