PHP全局变量

Question

I am breaking my head why the simplest thing is not working.

All I want is to access the variable declared in the included file.

I have file called connection.php in which I have a class called MySqlDatabase. In the bottom of the file I created the instance of the class and assiged it to variable called $database

// filename database.php begin

class MySqlDatabase(){

// code goes here

}

$database = new MySqlDatabase();

// filename database.php end

Now I included database.php in something.php and trying to access the $database variable like this

//something.php
require_once 'database.php';

function foo(){

global $database;

$sql = "some sql statement";
mysql_query($sql,$database->connection);
//and remainig code goes here...

}

When I run the something.php it is expected that the global variable $database should be available in the function foo() but it seems like the variable is null, I tested with is_object() function to check the object is available but it returning false.

For debugging purpose I added is_object() check in the database.php file and it is returning true.

Also I tried to access the global variable using other options like

$database =& $GLOBALS['database'];

But I still have no luck. I then printed the complete $GLOBALS array using print_r() function also but it doesnt have the $database variable, I also checked using get_defined_vars() but it also doesnt have the variable. But I am able to see them in the included file itself

I am breaking my head since two days to make this simple thing work but I compromised and copy pasting database connection code in all the files.

Answer 1

I made some change in your code, this work for me.

database.php

<?php
// filename database.php begin
class MySqlDatabase
{
    public $connection;
    function MySqlDatabase()
    {
        $this->connection= mysql_connect('HOST','USER','PASSWORD');
        mysql_select_db('databaseName',$this->connection);
    }
}
$database = new MySqlDatabase();
// filename database.php end
?>

something.php

<?php
require_once 'database.php';
function foo( )
{
    global $database ;
    $sql = "select * from tableName";
    $rs=mysql_query($sql,$database->connection);
    while($row=mysql_fetch_array($rs))
    {
        print_r($row);
    }
    //and remainig code goes here...
}
foo();
?>

You might be manipulating $connection variable in wrong manor.

Answer 2

If you have included the file then use the following:

//something.php
require_once 'database.php';

   /* Function FOO starts a new scope and doesn't see database object declared in database.php 
    * Therefore, you pass on the database object from calling function and use that instead.
    */

function foo($dbObj){     

    $sql = "some sql stagement";
    mysql_query($sql,$dbObj->connection);
    //and remainig code goes here...

}

foo($database);

Answer 3

There are only 3 possible reasons

• $database defined not in the global scope
• database.php being included not as a file
• some typo invisible to reader

Answer 4

您可以使用单例模式，也可以在数据库类中将变量设置为static。

Answer 5

Well, I figured out the problem. The issue is with the amfphp framework. This framework includes all my files (something.php). Its hard to explain it but in simple words I included the database.php in the one of the main php file related to the amfphp framework.

Thanks for you suggetions.