The latest summary of PHP interview questions and application questions

function fileShow($dir){                           
    $handle = opendir($dir);                     // 打开目录句柄
    while ($file = readdir($handle)) {           // 返回目录句柄中的条目
        if ($file !== '..' && $file !== '.') {
            $f = $dir . '/' . $file;
            if (is_file($f)) {
                echo &#39;|--&#39; . $file . &#39;<br>&#39;;     // 代表文件
            } else {
                echo &#39;--&#39; . $file . &#39;<br>&#39;;      // 代表文件夹
                fileShow($f);
            }
        }
    }
}

class db
{
    private        $con;
    private static $instance;

    /**
     * 定义一个私有的构造函数，确保单例类不能通过 new 关键字实例化，只能被其自身实例化
     */
    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);
    }

    /**
     * 创建单例
     */
    public static function getInstance($host, $username, $password, $database)
    {
        if (self::$instance) return self::$instance;
        self::$instance = new db($host, $username, $password, $database);
    }

    /**
     * 关闭数据库连接
     */
    public function close()
    {
        return mysqli_close($this->con);
    }

    /**
     * 定义私有的__clone()方法，确保单例类不能被复制或克隆
     */
    private function __clone()
    {
    }
}

$url = "http://www.phpres.com/index.html";
$str = file_get_contents($url);

// 或 
$ch=curl_init();
curl_setopt($ch,CURLOPT_URL,$url);
curl_setopt($ch,CURLOPT_HEADER,0);
curl_exec($ch);
curl_close($ch);

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

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

function get_ext1 ($file_name) {
    return strrchr($file_name, '.');                     // .jpg
}

function get_ext2 ($file_name) {
    return substr($file_name, strrpos($file_name, '.')); // .jpg
}

function get_ext3 ($file_name) {
    $tmp = explode('.', $file_name);
    return array_pop($tmp);                              // jpg
}

function get_ext4 ($file_name) {
    return pathinfo($file_name, PATHINFO_EXTENSION);    // jpg
}

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

header('location:index.php');     // 跳转页面
header("HTTP/1.1 404 Not Found"); // 实现页面404错误提示功能

# $str是一段html文本
$pattern = &#39;/<script.*>.*<\/script>/i&#39;;
preg_replace($pattern,&#39;&#39;,$str);

$arr = array("",1,2,3,"");
$ptn = "/\S+/i";  
print_r(preg_grep($ptn,$arr));

function dayCount($year, $month) {
    echo date('t', strtotime($year . '-' . $month . '-1'));
}

function get_last_month_last_day(){
    $date = "2021-2-18";
    $time = strtotime($date);
    $day  = date('j',$time); // 获取该日期是当前月的第几天
    return date('Y-m-d',strtotime("-{$day} days",$time));}

$fp = fopen("lock.txt","w+");
if(flock($fp, LOCK_EX)) {          // 写锁
    fwrite($fp, "write something");
    flock($fp, LOCK_UN);           // 解锁
} else {
    echo "file is locking";
}
fclose($fp);

 $str     = '08/26/2003';
 $pattern = '/(\d+)\/(\d+)\/(\d+)/';
 $rep     = '$3-$1-$2';
 echo preg_replace($pattern, $rep, $str);

// 方法一:用DateTime类
$day1 = '2003-09-16';
$day2 = '2011-11-23';
$d1 = new dateTime($day1);
$d2 = new dateTime($day2);
echo $d1->diff($d2)->days;

// 方法二,用时间戳计算
echo (strtotime($day2) - strtotime($day1))/(86400);