Global variable in all class functions

My understanding of the question is that it is necessary to save the connection data in a variable that can be accessed from anywhere in the application. A global variable is a solution to this but in fact it is not good to use it.

So the solution is to encapsulate the non-global variable into a function by maintaining its static state or using an approach considered more modern, but not necessarily better, by encapsulating the variable in a static class.

class Conexao {
    private static $conexao = "dados da conexao aqui - classe";
    public static function PegaConexao() {
        return self::$conexao;
    }
}

function conexao(){
    static $conexao = "dados da conexao aqui - funcao";
    return $conexao;
}

class Uso {
    public function AbreBanco1() {
        echo conexao() . "\n";
    }
    public function AbreBanco2() {
        echo Conexao::PegaConexao();
    }
}

Uso::AbreBanco1(); //chama só para demonstrar
Uso::AbreBanco2(); //chama só para demonstrar

See running on ideone .

As the question does not give details I can only show a generic solution but it is easy to adapt to use according to the specific need.

It does not have to have both ways, I put both to exemplify, obviously only a AbreBanco() would exist. And the contents of the variable will probably be different.

Create accessible variable for all functions of a class:

<?php

    class teste {

        /* construct */
        function __construct($variavel) {

            $this->global_variavel  = $variavel;

        }

        function checando_funcao() {

                echo $this->global_variavel;

        }

        function checando_funcao2() {

                echo $this->global_variavel;

        }

?>

• To run a test:

      //Criando uma nova instância
  
      $variavel = 'Meu texto!';
      $a = new teste($variavel);
  
      //Executando as duas funções com os mesmos valores de uma única variável "global"
      $a->checando();  
      $a->checando_funcao2();
  

Note:

  

To ensure reverse compatibility, if PHP 5 can not find a __construct () for a given class, it will look for the old-fashioned constructor function, which has the same class name. Effectively, it means that the only case that can cause compatibility problems would be if the class has a method called __construct () that is used for another purpose that does not initialize the object.

To make a variable member of the class set the access modifier and then its name

public - is accessible by all methods of the class and outside of it as well.

protected - accessible only within the class and its derivatives.

private - accessible only to the methods of the class.

class Teste{
   public $variavel = 'esse valor pode ser modificado externamente';

   public function foo(){
     echo $this->variavel;
   }
}