PHP在启动时加载一个函数

I am doing some PHP programming and have a question: How can I load a PHP function when the PHP script is first run, and only when it is first run?

thanks

You can use a Lock file

$lock = "run.lock" ;

if(!is_file($lock))
{
    runOneTimeFuntion(); //
    touch($lock);
}

Edit 1

One Time Function

runOneTimeFuntion ();
runOneTimeFuntion ();
runOneTimeFuntion ();
runOneTimeFuntion ();
runOneTimeFuntion ();
runOneTimeFuntion ();
runOneTimeFuntion ();
runOneTimeFuntion ();

function runOneTimeFuntion() {
    if (counter () < 1) {
        var_dump ( "test" );

    }

}

function counter() {
    static $count = 0;
    return $count ++;
}

Output

string 'test' (length=4)

EACH time you start php script he starts as a new one, no matter how much times it was called befor.

And if you aware of re-declare functions, which is forbided in PHP, load functions from external fles useing:

<?php require_once(my_function_file.php); ?>

If you want scrpt remember if he was called befor, it's possible to do using some form of logging (data base\file) and cheacking it befor load... But I don't see any reason for this in case of function load...

Or use a plain boolean...

$bFirstRun = true;

if( $bFirstRun ) {
    run_me();
    $bFirstRun = false;
}

There is a PHP function called function_exists

You can define your own function within this function, and then you could see whether this exists or not.

if (!function_exists('myfunction')) {
  function myfunction() {
    // do something in the function
  }
  // call my function or do anything else that you like, from here on the function exists and thus this code will only run once.
}

Read more about function_exists here: http://www.php.net/function_exists