在PHP中运行代码一次

I'm trying to write a class in PHP that acts as a wrapper for a collection of command line tools to make them easier to use from PHP.

I have a single class (MyClass) in a file myclass.php.

I have code that checks to see if the required tools are installed and then sets a constant (TOOLS_AVAILABLE) to either true or false. Although it's not a lot of code, I only want it to run the first time somebody tries to instantiate my class or use any of its static functions. What's the best practice for handling this?

I only want it to run the first time somebody tries to instantiate my class or use any of its static functions.

Well, the best answer is not to have any static methods. Then you can stick the code in a constructor method as per the answer by @treegarden.

If you must have static methods, then you'll need a static flag within the class to indicate when you've called the 'run once' code, so you can avoid running it again. And then call it explicitly from each of your static methods and the constructor. Something like this:

<?php
class myClass {
    private static $hasRunOnce = false;

    private static runMeOnce()
    {
        if (!self::$hasRunOnce) {
            self::$hasRunOnce = true;
            //put your 'run once' code here...
        }
    }

    public static oneOfYourStaticMethods()
    {
        self::runMeOnce();
        //put your static method code here...
        //this would be the same for each of your static methods and your constructor.
    }
}

Hope that helps.

You need to create a __construct function in your class and put whatever code you want to execute on instantiation in there:

class MyClass {
    function __construct(/* arguments */) {
        /* your code here */
    }
}

The code will get executed only once when someone instantiates the class.