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Hoose
Asked: 2020-10-21 14:51:23 +0800 CST 2020-10-21 14:51:23 +0800 CST

Make variable global inside a function

  • 772

I have two files, one called connection.php and one called suggest.php, in connection.php I do the connection perfectly with a function called connectDB and I use it without any problem in suggest.php.

However, I have another function in which I want to display the information from my database with a SELECT, and I would like to do it through a function as well. The error that PHP throws me is the following:

Fatal error: Call to a member function query() on null in C:\AppServ\www\object\db\inc\connection.php on line 18

I am not very expert but I think it has to do with the scope of the variable, since within the connectDB function there is the variable (object) $db.

Can I make that variable global so I can use it in all functions? How can I do it?

suggest.php

<?php 
  include 'connection.php';

  connectDB('root','administrador');
  selectMedia();
?>

connection.php 

  function connectDB($user, $pass, $dsn = 'mysql:host=localhost;dbname=database'){
    try {
      $db = new PDO($dsn, $user, $pass);
      $db->setAttribute(PDO::ATTR_CASE,PDO::CASE_UPPER);

    } catch (Exception $e) {
      echo "Error: " . $e->getMessage()."<br>";
      echo "Código de excepción: " . $e->getCode()."<br>";
      echo "Línea fuente: " . $e->getLine()."<br>";
      echo "Archivo: " . $e->getFile();
    }
  }

  function selectMedia(){
    try {
      $results = $db->query("SELECT title, category FROM Media");
      echo "Cool!";
    } catch (Exception $e) {
      echo "Error: " . $e->getMessage();
    }
  }

  ?>
php

5 Answers

  1. Best Answer

    Creating a variable global is not a good practice / Globals are evil

    You can create a file globalwhere you store for example all your essential functions for your application, in this case it would be for example the configuration to connect to your database connectDB(...).

    connection.php

    <?php

$dsn  = 'mysql:host=localhost;dbname=database'
$user = 'root'
$pass = 'administrador' 


function connectDB($user, $pass, $dsn){

    try {
        $db = new PDO($dsn, $user, $pass);
        $db->setAttribute(PDO::ATTR_CASE,PDO::CASE_UPPER);

    } catch (Exception $e) {
        echo "Error: " . $e->getMessage()."<br>";
        echo "Código de excepción: " . $e->getCode()."<br>";
        echo "Línea fuente: " . $e->getLine()."<br>";
        echo "Archivo: " . $e->getFile();
    }
}

// Aquí lo llamas solo una vez
$db = connectDB($user, $pass, $dsn);


//.... más funciones

function selectMedia($db){

    try {
        $results = $db->query("SELECT title, category FROM Media");
        echo "Cool!";
    } catch (Exception $e) {
        echo "Error: " . $e->getMessage();
    }
  }

    Once the file is created, globalyou include it in any file where you always need it.

    anyFile.php

    <?php

// cambiado a require_once
require_once 'connection.php';  

selectMedia($db);

otraFuncionQueNecesitaDB($db);
    • 2

  2. A single dimension to the solution proposed by @aldanux, if your connection.php file is called in several files, I recommend you use include_once

    include_once 'connection.php';

    This does exactly the same thing as a normal include, but if your file was already included, it doesn't include it again, this will avoid errors due to variables already defined.

    • 1

  3. More elegant would be to create a class, in a separate .php, and use the singleton pattern to have a single instance of the object you want to create (in this case your supposed global variable) so that you can always access it from anywhere and that is always instantiated and with a unique value for the entire project. I leave you a link to guide you: https://www.uno-de-piera.com/el-patron-singleton-en-php/

    • 0

  4. Maybe you are complicating yourself in vain? I think you would solve everything with a simple return in your function:

    function connectDB($user, $pass, $dsn){
  try {
    $db = new PDO($dsn, $user, $pass);
    $db->setAttribute(PDO::ATTR_CASE,PDO::CASE_UPPER);
    return $db;

  } catch (Exception $e) {
    echo "Error: " . $e->getMessage()."<br>";
    echo "Código de excepción: " . $e->getCode()."<br>";
    echo "Línea fuente: " . $e->getLine()."<br>";
    echo "Archivo: " . $e->getFile();
    return false;
  }
}
    • 0

  5. Something simpler and less complication, above all we get a functioncleaner is to create a config.ini.php file

    And in the PHP document that requires database connections, call them viainclude_once

    include_once 'config.ini.php';

    Inside the file you create the connection, imagining that the variable $conhas the values ​​of the connection.

    It would only suffice to add one of the PHP global reserved words to thefunction

    Example:

    function selectMedia(){...
  global $con; //Con esto ya tendrías los valores de la conexión

   // Código
}
    • 0