Require_once doesn't seem to affect all functions?

Question

Everything was working fine in my little project, until I decided to clean up a little bit and moved database-related php-files to their own folder. Then things went strange.

I am trying to use two functions here:

function getEntries () {
    require_once("mysqliVariables.php");
    $mysqli = new mysqli($dbHost, $dbUname, $dbPwd, $dbName);           
    $sql = "statement...";
    $result = $mysqli->query($sql) or die($mysqli->error);

    echo $dbHost; // prints host
    return $result;
}

function getBiggestMonth () {
    require_once("mysqliVariables.php");
    $mysqli = new mysqli($dbHost, $dbUname, $dbPwd, $dbName);           
    echo $dbHost; // prints nothing! why?       

    $sql = "statement...";
    $result = $mysqli->query($sql) or die($mysqli->error); // this line does not run, of course.

    return $result;
}

I use another function in a different file (and folder) to call these functions, that starts like this:

function listTasks() {      
    require_once("db/mysqliFunctions.php");

    // Get entries using mysqli.
    $tasks = getEntries();

    echo "<pre>";
    var_dump($tasks);
    echo "</pre>"; // program works fine this far.

    $bm = getBiggestMonth(); // program breaks somehow during this function call.

My variables are in a php-file like so:

<?php   
$dbHost = "host";
$dbUname = "username";
$dbPwd = "password";
$dbName = "databasename";

?>

If I switch the funtion's call order, then getBiggestMonth() runs fine and the other one won't. Also, all of this worked fine when all the files were located in the same folder (the functions were then static functions inside a class, but that shouldn't be an issue, the same problem persists here), so I dont understand how possible variable scope can be different here, and require_once should take care of other things. Help?

Answer 1

This is because you are using require_once. It will only include the configuration once. You can change it to use require so that it will work as you expect.

The require_once() statement is identical to require() except PHP will check if the file has already been included, and if so, not include (require) it again.

You are using require_once to pull in a file into the scope of the getEntries() function. PHP keeps a record of the files that have been required in so when you then call require_once in getBiggestMonth() it knows it has already been included in getEntries(). Because it has already been included it does not require the file in again so you don't get your variables in your getBiggestMonth() scope.

require_once does not have anything to do with variables it just monitors the files that have been included into the current PHP process.