PHP - Variable static to a function

Question

In C we can do (if I remember well) that :

void foo()
{
    static bool firstCall = true;

    if(firstCall)
    {
        // stuff to do on first call

        firstCall = false;
    }

    // more stuff
}

I would like to do that in PHP to avoid my models to query the database more than once when the same method is called more than once.

class User
{
    public static function & getAll($reload = false)
    {
        static $result = null;

        if($reload && null === $result)
        {
            // query the database and store the datas in $result
        }

        return $result;
    }
}

Is it allowed ? Does it work ? Is it compatible with PHP < 5.3 ?

If yes then i have another question :

Say we have several methods common to all models, i would group them in an abstract base class :

abstract class AbstractModel
{
    public static function & getAll($tableName, $reload = false)
    {
        static $result = array();

        if($reload && !isset($result[$tableName]))
        {
            // query the database depending on $tableName,
            // and store the datas in $result[$tableName]
        }

        return $result[$tableName];
    }
}

class User extends AbstractModel
{
    public static function & getAll($reload = false)
    {
        $result = parent::getAll('users', $reload);
        return $result;
    }
}

class Group extends AbstractModel
{
    public static function & getAll($reload = false)
    {
        $result = parent::getAll('groups', $reload);
        return $result;
    }
}

Would this work too ? Could it be improved ?

Thanks for your help :)

Unrelated: Why are you returning references? You should let PHP optimize the code, you don't usually have to do it. — Ruan Mendes
– Ruan Mendes, Commented Dec 5, 2012 at 23:54
I generally return arrays which, if i understood well, are considered as a primitive type, and copied. Am I wrong ? — Virus721
– Virus721, Commented Dec 5, 2012 at 23:55
The compiler will optimize it not to copy the array as long as you're not modifying it. — Ruan Mendes
– Ruan Mendes, Commented Dec 6, 2012 at 0:03
@JuanMendes Is that a new feature? I've had trouble of arrays being copied as well. You could solve it by passing them by reference, or wrapping them in a class. — GolezTrol
– GolezTrol, Commented Dec 6, 2012 at 0:05
See php.net/manual/en/language.references.return.php Do not use return-by-reference to increase performance. The engine will automatically optimize this on its own. Only return references when you have a valid technical reason to do so. — Ruan Mendes
– Ruan Mendes, Commented Dec 6, 2012 at 0:06

Sherif · Accepted Answer · 2012-12-06 00:35:16Z

2

Yes, you can do that. It is supported as of PHP 5.0.0.

To clarify I would like to distinguish between two very different things in PHP that both use the static keyword. First, is the class static scope, which belongs specifically to the entire class. Second, is the variable static scope, which specifically belongs to the local scope of a function.

This is the class static scope (this is available only in PHP >= 5.3.0):

class Foo {
    public static $var;

    public static function GetVar() {
        return ++static::$var;
    }
}

var_dump(Foo::GetVar(),Foo::GetVar());

The above code would give you int(1) int(2) which is what you are expecting.

This is the variable static scope (this is available in PHP >= 5.0.0):

class Foo {
    public static function GetVar() {
        static $var = 0;
        return ++$var;
    }
}

var_dump(Foo::GetVar(),Foo::GetVar());

The above code would also give you int(1) int(2) which is also what you are expecting.

Notice that one belongs specifically to the function's local scope (even if that function is a class member) and the other belongs specifically to the class.

Also notice I used the static keyword in my first example and not the self keyword, since self does not allow you to do LSB (Late Static Binding). This is likely something you're going to need to take into consideration when you're inheriting and then calling on the parent class and especially if you're going to be using class static variables and not static variables in the function's local scope.

answered Dec 6, 2012 at 0:35

Sherif

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4 Comments

Virus721 Over a year ago

Thanks for your answer. This one seems a bit more accurate about what i was wondering so i'll change the accepted answer :p Also do you recommend me the class or the variable static scope to do that ?

Sherif Over a year ago

It depends on what your intentions are. If what you want isto store that static variable in the function's local scope then go with the variable static scope. With that you can only get at the variable from inside that function. If you want to share that variable with other functions in your class then go with the class static scope, because then you don't have to call that function to get the variable.

Sherif Over a year ago

I ran out of room so I had to add this part "You can also specify the visibility of the class variable with the public, private, or protected keywords. This makes the variable either available to everyone (public), only to the class and its children (protected), or only to that class (private)."

Virus721 Over a year ago

I know that thank you ^^ I've been using PHP for a year, just never met problems involving variable static scope before that :p

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