How to use static and global variables in PHP?

Question

I need the value of a variable in several functions to increment and decrement the value of the variable.

I have tried using static variable started with null value, but even changing its value, it gets null value.

How do I manipulate her?

Answer 1

How to use global variable? Simple, do not use.

Global variables are problematic. It is difficult to ensure that it will not be confused with other variables. It’s hard to understand who and when she’s being altered.

Static variable

Simply declare the variable to static (static). This way it will have life throughout the application. If it is within a function its visibility will be only within the function and this is important. But it doesn’t stop her from having life throughout the execution.

When variable is declared static it is stored in a different region of memory than it is lost when function ends as is the case for local variables within a function.

Here’s a possible algorithm for your counter. You can certainly improve it. You can even make the increment happen within the function if that’s all you want. You can use creativity and do it in many different ways. The important thing is that now knows that it is possible to extend the life of the variable throughout the life of the application without exposing it to every application, which would be a beautiful of a bad practice.

function contador($valor) {
    static $contador;
    if (isset($valor)) {
        $contador = $valor;
    }
    return $contador;
}

echo contador(1) . "\n";
$contador = contador(null) + 1;
echo contador($contador);

Behold working in the ideone. And in the repl it.. Also put on the Github for future reference.

That is to say global state. The ideal is not to use even this. But depending on the application it does not cause real problem.

---

Rafael Withoeft’s answer also gives another possible solution without using global or static. The only difficulty of it is that it would have to pass the state variable throughout the application to use elsewhere. The variable has no extended lifespan outside the function where it was created. This can be bad but it can also be good. In some cases - this does not seem to be the case for AP - this may be the best option. This is a shape similar to the use of an object. Only the object has only one member inside, the value itself.

Answer 2

You can use reference. Example:

<?php
function foo (&$var)
{
    $var++;
}

$a=5;
foo ($a);
// $a é 6 aqui
?>

Source: http://php.net/manual/en/language.references.pass.php

What references do? http://php.net/manual/en/language.references.whatdo.php

Answer 3

Example of use of global variables !!

<?php
    $teste = "Variável 1";
    $teste2 = "teste2";
    function teste(){
        global $teste,$teste2;
        echo $teste; // Retorno será Variável 1
    }

    //Chamando a função
    teste();
    //Alterando valor da variável...
    $teste = "valor alterado...";
    teste();
?>