Connection is not defined - php

Question

I have the following code
<?php
$host = "localhost";
$dbname = "hawkI";
$user = "root";
$password = "";
$userExist = false;
$userIP = null;
$userHasFinish = null;
$userLastPage = null;
try {
$dbh = new PDO('mysql:host='.$host.';dbname='.$dbname, $user, $password);
} catch (PDOException $e) {
echo 'Connection failed: ' . $e->getMessage();
}
function getIPforBDD(){
return $_SERVER['REMOTE_ADDR'];
}
function UpdateUserProfile()
{
$requete = "SELECT * FROM users WHERE ip = ".getIPforBDD();
$result = $dbh->query($requete);
if($resultat->rowCount() == 0)
exit();
foreach($result as $ligne)
{
$userIP = $ligne['ip'];
$userhasFinish = $ligne['finish'];
$userLastPage = $ligne['lastPage'];
}
}
function CheckUserPosition()
{
UpdateUserProfile();
if(!$userExist)
AddUser();
return GetUserStatus();
}
function GetUserStatus()
{
$page;
if($userHasFinish)
$page = "end.php";
else
$page = $userLastPage;
return $page;
}
function AddUser()
{
$requete = "INSERT INTO users (ip, finish, lastPage) VALUES (".getIPforBDD().", ".false.", questionnaire_initial.php)";
$result = $dbh->query($requete);
}
function SavePageInBDD($page){
$requete = "UPDATE users SET lastPage = '.$page.' WHERE ip = ".getIPforBDD();
$result = $dbh->query($requete);
}
?>
But, I have a problem when I use it
( ! ) Notice: Undefined variable: dbh in C:\wamp64\www\HawkI\bdd.php
on line 66
I do not understand correctly how PHP work it's the first time I use it, but I tried to make
global $dbh = new PDO('mysql:host='.$host.';dbname='.$dbname, $user, $password);
That doesn't work too.
Also, it seems that value that are put outside of functions are not global like it would be in js, how can I make something accessible from everywhere (like file that include that file)
Thanks

Answer 1

Better way would be to do something like this:
function getDB(){
$dbh = null;
try {
$dbh = new PDO('mysql:host='.$host.';dbname='.$dbname, $user, $password);
} catch (PDOException $e) {
echo 'Connection failed: ' . $e->getMessage();
}
return $dbh;
}
And than in your functions do this:
function AddUser()
{
$dbh = getDB();
if(!is_null($dbh)){
$requete = "INSERT INTO users (ip, finish, lastPage) VALUES (".getIPforBDD().", ".false.", questionnaire_initial.php)";
$result = $dbh->query($requete);
}
}

Answer 2

To use $dbh inside a function, you need to include global keyword inside the function scope.
You can find the global keyword explanation here http://php.net/manual/en/language.variables.scope.php#language.variables.scope.global
function AddUser()
{
global $dbh;
$requete = "INSERT INTO users (ip, finish, lastPage) VALUES (".getIPforBDD().", ".false.", questionnaire_initial.php)";
$result = $dbh->query($requete);
}

Answer 3

You may use like this
$host = "localhost";
$dbname = "hawkI";
$user = "root";
$password = "";
$userExist = false;
$userIP = null;
$userHasFinish = null;
$userLastPage = null;
$dbh = NULL;
function db () {
try {
if ($GLOBALS['dbh']===NULL){
$GLOBALS['dbh'] = new PDO('mysql:host='.$host.';dbname='.$dbname, $user, $password);
}
return $GLOBALS['dbh'];
} catch (PDOException $e) {
echo 'Connection failed: ' . $e->getMessage();
}
}
function SavePageInBDD($page){
$dbh = db();
$requete = "UPDATE users SET lastPage = '.$page.' WHERE ip = ".getIPforBDD();
$result = $dbh->query($requete);
}