如果PHP脚本已经运行，请不要再次运行它

Question

I am reading data from the sheet and want to implement singleton in my process so that I can run read function, one at a time. but i got to know that i cant do that with singleton so how can i do that without using mutex or semaphore.

I have written a code for the same which calls the class and set a static variable and then call the function to check if it has the class, so if the class is there then don't run the read function.

class DataParser extends config {

   private static $_instance = false;

   public static
   function getInstance() {
    if (self::$_instance == false) {
     print_r("expression");
     self::$_instance = true;
     return self::$_instance;

    }
    return false;
   }

   function __construct($params) {}
}

$dataParser = new DataParser($confData);
$p = DataParser::getInstance();
if ($p) {
   $res = $dataParser - > read();

}

I want to run the read function one at a time, if one read is running then the other read will not run using php dont want to use mutex or semaphore

Answer 1

Are you using a database in your app? Is the reader task running in a distributed environment or always on the same server? I suggest looking into advisory locking. Both MySQL and PHP supports it.

It would look something like this using an exclusive lock on file in PHP.

class DataParser extends config {

   private static $_instance = false;

   public static
   function getInstance() {
    if (self::$_instance == false) {
     print_r("expression");
     self::$_instance = true;
     return self::$_instance;

    }
    return false;
   }

   function __construct($params) {}
}


$dataParser = new DataParser($confData);
$p = DataParser::getInstance();

$fp = fopen("/tmp/.lock", "r+");

if ($p && flock($fp, LOCK_EX)) {  
    $res = $dataParser->read();
    flock($fp, LOCK_UN);    
} else {
    // Skip silently or do something else?
}

fclose($fp);