mysql_connect和mysql_selectdb没有将一些变量作为参数的奇怪问题

Question

I was working in some code in a PHP course I assisted, in a LAMP environment, and worked without problems. After the course, I took my code home and ran it on a WAMPServer, and for some reason, mysql_connect is not accepting some variables as arguments. I know this because I tried giving the parameters to mysql_connect by hand and the connection works. Also, I echoed all four variables and they print out OK.

I am new to PHP, but this doesnt make any sense to me.

The code:

functions.php

 <?php

require ("config.php");
     function conectardb () { 
     mysql_connect ($server, $login, $pass);
     mysql_select_db ($db);
 }

?>


config.php

<?php
 $login = "root" ;
 $pass = "" ;
 $server = "localhost";
 $db = "testing";
?>

I've tried replacing the plain arguments by their variables one by one, and found out the code works until this point:

 function conectardb () { 
     mysql_connect ($server, "root", $pass);
     mysql_select_db ("testing");
 }

If I use $login or $db, the connection will not work. Any ideas? This is driving me crazy.

Answer 1

This is a misunderstanding of scope in PHP.

Functions exist in their own scope. You defined $login, $pass, etc. in a different scope than the function. The function can't access them, it can't see them.

You can do a couple things about this:

1. Define the database connection parameters as constants instead of variables
2. Define the variables within the function (requiring the configuration file inside the function will have the same effect)
3. Use the global keyword to pull them from the global scope into the function scope

i.e.

$bar = 'hello world';
function foo() {
    global $bar;
    echo $bar;
}