关于设置PHP类只有一次的方法的反馈

and would like to work with them effectively. Here is the premise for an application I am doing:

1. we only need to instantiate a class once
2. I don't know necessarily if the class has been instantiated
3. If I ever need to instantiate a class multiple times, I'll have enough common sense not to use this system
4. the class could be called in another class, function etc., but once called I want it to be available anywhere

that said here is a function I am working on. It allows a class to be set, once, and be available globally anywhere. But it seems very clumsy and and I think there must be improvements in it:

            function set_class_once(){
                //example of most complex use: set_class_once('ClassA',$a [array], '$ginger', 'string');
                $args=func_get_args();
                if(!count($args))return;
                $i=0;
                $class='';
                foreach($args as $n=>$v){
                    $i++;
                    if(!$class){
                        $class=$v; //always a string
                        unset($args[$n]); //remove from $args
                        continue;
                    }
                    if(is_array($v)){
                        $temp[$i]=$v;
                        $args[$n]='$temp['.$i.']'; //re-task
                    }else if(substr($v,0,1)=='$' && substr($v,1,7)!='GLOBALS'){
                        $args[$n]='$GLOBALS[\''.str_replace('$','',$v).'\']'; //variable
                    }else{
                        $args[$n]='\''.addslashes($v).'\'';         
                    }
                }
                if(isset($GLOBALS[$class]) && is_object($GLOBALS[$class])){
                    //OK, we've instantiated that class
                }else if(!class_exists($class)){
                    //fatal error
                    exit('Class '.$class.' does not exist');
                }else{
                    print_r('$GLOBALS[$class]=new '.$class.'('.(!empty($args)?implode(',',$args):'').');').'<br>';
                    eval('$GLOBALS[$class]=new '.$class.'('.(!empty($args)?implode(',',$args):'').');');
                }
            }

            class ClassC{
                function ClassC($param1,$param2,$param3){
                    echo 'here is param1:<br>';
                    print_r($param1);
                    echo 'here is param2:<br>';
                    print_r($param2);
                    echo 'here is param3:<br>';
                    print_r($param3);
                }
            }


            //with no params passed set_class_once('ClassA');
            //with params passed:
            $a=array(
                'apple'=>'red',
                'spinach'=>'green',
            );
            $ginger='fred backwards';
            set_class_once('ClassC',$a,'$ginger','string');

Build yourself a simple singleton and extend it for the classes that you want to have only 1 instance:

class Singleton
{
    public static function getInstance()
    {
        static $instance = null;

        if (null === $instance) {
            $instance = new static();
        }    
        return $instance;
    }

    protected function __construct() { }
}

class ClassC extends Singleton
{
}

Then:

$object = ClassC::getInstance();

Not sure that I follow the args logic, but I'm sure there is a better practice for what you are attempting. Maybe create these with a factory class?