PHP experience system // simple - php

Question

As a begginer in php programming language i'm playing with the code, working on localhost and i did some little projects.Now i am trying to do an experience system as simple as i can, i am stuck at this part and i don't know what i am doing wrong.Some suggestions?
What i am doing wrong?
The code.
function update_user_xp($user_id, $xp_ammount){
global $db;
$params = array('user_id' => $user_id);
$users = $db->rawQuery("SELECT * FROM users_xp WHERE user_id = ?", $params);
$data = array(
'user_xp_amount' => $xp_ammount + $users[0]['user_xp_amount'],
'user_id' => $user_id
);
$db->where ('user_id', $data['user_id']);
if ($db->update ('users_xp', $data)){
$xpReceived = 'You have received '.$xp_ammount.' points of experience! Have a total of '.$data['user_xp_amount'].' points of experience.';
} else {
$xpReceived = $db->getLastError();
}
return $xpReceived;
}
//update_user_xp(4, 10); // user_id: 4, update with 10 points
function get_user_xp ($user_id){
global $db;
$params = array('user_id' => $user_id);
$user = $db->rawQueryOne ('SELECT * FROM users_xp WHERE user_id=?', $params);
$xp = $user['user_xp_amount'];
return $xp;
}
function xp_need () {
global $db;
$xpBarNeed = $db->rawQuery("SELECT `level`, `expneeded` FROM `experience_level`");
foreach ($xpBarNeed as $key => $value) {
$output[] = $value;
}
return $output;
}
$xpn = xp_need();
$userXP = get_user_xp(4);
for($i = 0; $i < count($xpn); $i++){
if($xpn[$i]['expneeded'] == $userXP)
{
//This part is working well
print 'You are level <b>' . $xpn[$i]['level'].'</b>';
} else {
if ($userXP > $xpn[$i]['expneeded'] && $userXP >= $xpn[$i]['expneeded'])
{
//This is the part that doesn t work,
$diffEXP = $xpn[$i]['expneeded'] -= $userXP;
print 'You need more exp '. $diffEXP.'</br>';
}
}
}
This is how i am seeing in the page.
https://prnt.sc/u7z18u

Answer 1

Please note that my solution is not the best or say a well-optimized solution at the time of writing. I will try to optimize it in the near future. For the time being, you can use this:
<?php
$xpn = xp_need();
$userXP = get_user_xp(4);
$level = 0;
$nextExp = 0;
for ($i = count($xpn) - 1;$i >= 0;$i--)
{
if ($userXP >= $xpn[$i]['expneeded'])
{
$level = $xpn[$i]['level'];
$nextExp = $xpn[$i + 1]['expneeded'];
break;
}
}
$expNeeded = $nextExp - $userXP;
$percentage = round(($userXP/$nextExp) * 100);
echo "Current level: " . $level;
echo "<br/>Exp needed for the next level (" . ($level + 1) . "): " . $expNeeded;
echo "<br/>Exp achieved percentage for the next level: " . $percentage;
?>