我編寫的php代碼錯誤無法理解如何糾正？

Question

class Logging{   

    private $log_file = 'c:/xampp/htdocs/jcert2/tmp/sslogfile.txt';   
    public  static $fp = null;

    public static function lwrite($message){   
    if (Logging::fp) Logging::lopen();   
  //  $script_name = pathinfo($_SERVER['PHP_SELF'], PATHINFO_FILENAME);   
    $time = date('H:i:s');   
    fwrite(Logging::fp, "$time $message\n");   
  }   
  // open log file   
  private static function lopen(){   
    $lfile = $this->log_file;   
    $today = date('Y-m-d');   
    Logging::fp = fopen($lfile . '_' . $today, 'a') or exit("Can't open $lfile!");   
  }   
}

我創建了一個日志文件，最后一行出現錯誤

Logging::fp = fopen(....)

錯誤是意外錯誤'='可以指導我理解和糾正錯誤。

Answer 1

雙冒號表示該類的靜態屬性。 您不能將值分配給類的靜態屬性。 有關靜態屬性的更多信息，請參見：

http://php.net/manual/zh/language.oop5.static.php

Answer 2

缺少$：Logging :: $ fp = fopen（$ lfile。'_'。$ today，'a'）或exit（“無法打開$ lfile！”）;

Answer 3

您可以使用getter / setter

class Logging{   

    private $log_file = 'c:/xampp/htdocs/jcert2/tmp/sslogfile.txt';   
    private $fp = null;

    private static function lopen(){   
        $lfile = $this->log_file;   
        $today = date('Y-m-d');   
        $this->fp = fopen($lfile . '_' . $today, 'a') or exit("Can't open $lfile!");   
    }

    public static function get_fp(){
        return $this->fp;
    }
}