PHP Auto Aging Task for MyBB - php

Question

So, I was wondering if anybody would mind checking over this task and correcting it? I'm very sure I've muddled Python in with what little PHP I know, and that there are open tags.
Basically, there'll be a field where the nasty decimal age goes ($age, which will later be replaced by the appropriate field id). Our site works in months for juveniles and then years and seasons for adults. Using the nasty age, I'm trying to calculate the rounded age values and then store them as a string value which will then be set as the value of the field that will display the age ($displayagefid, will be replaced later with the appropriate field id). Only certain usergroups will be updated (the list is huge, so I left it out).
I also have no idea how to set a variable as a string using both string and the value of another variable.
Please know that I'm a complete newbie to PHP.
This is intended to run as a task on a self-hosted MyBB forum.
Thank you in advance!
<?php
function task_age($task)
{
global $mybb, $db;
$increment = 0.04167
$age = $age + $increment
floor($age*4) = $seasons
floor($age) = $years
floor($age*12) = $months
if ($year < 1) {
$display_age = $months, "mnths"
}
elseif ( ! filter_var($year, FILTER_VALIDATE_INT) ){
$display_age = $year, "yrs"
}
else {
$display age = $display_age = $years, "yrs", $seasons, "s"
};
$query = $db->query("
UPDATE mybb_userfields userfields
for ($usergroup = a || b || d || all that other crap) {
SET $dispalyagefid = $display_age;
};
");
add_task_log($task, "The age characters task successfully ran.");

Answer 1

I had a cursory look over your code and the first thing which sticks out is you have some of your variable assignments back to front:
$increment = 0.04167
$age = $age + $increment
floor($age*4) = $seasons
floor($age) = $years
floor($age*12) = $months
Whatever is on the left gets set to whatever is on the right, so your first two are OK but the last three need switching around.
Having said that it seems to me you are not approaching this correctly. I enter my decimal age into your site but how are you going to work out seasons? It might be my birthday tomorrow, it might have been my birthday yesterday.
You would be better off having the user enter a date of birth, from that calculate their age.
$birthday=date_create("2013-03-15");
$today=date_create('now');
$diff=date_diff($birthday,$today);
Now in the $diff variable you can check all the elements of a PHP date. So first check if they are under 18:
if ($diff->format("%y") < 18) {
$ageInMonths = ($diff->format("%y") * 12) + $diff->format("%m");
$age = "$ageInMonths months";
}
If they are over 18 you want age in years, then calculate seasons from the remaining months.
else {
$ageInYears = $diff->format("%y");
$ageInSeasons = floor($diff->format("%m") / 4);
if ($ageInSeasons > 0) {
$age = "$ageInYears years and $ageInSeasons seasons";
} else {
$age = "$ageInYears years";
}
}