Use a parameter as an index in PHP - php

Question

I am trying to do a thing that I dont know if can work. Also accept other ideas.
I have an array passed as a parameter where the index is the task id in the database and the value is the last syncronization for the task with the database
$sync=Array
(
[22805] => 1406822699
[22806] => 1406824500
[22807] => 1406838670
)
Then I do a select in the database which gives me the whole of tasks and I one to update on the database only some tasks, basically the ones that are out of date.
//$tasks is the list of all tasks from the database and $sync is the array which is pased by the user
foreach($tasks as $task)
{
if($task['sync']<=$sync[$task['taskList_id']])
{}
else
{//to be updated
$taskModel->updateLastSync($task['taskList_id'],$time);
$task['sync']=$time;
}
}
This is the problematic line and what I need to know how to do.
$sync[$task['taskList_id']]
I want to use a parameter as index to get the value of an array.
How can I achieve this.
Because this other idea is another foreach for $sync inside the foreach for $tasks

Answer 1

Without seeing the full script or having access to var_dump at certain locations it's hard to say what's going on but here are some things to check:
Make sure you're getting results from the database query and that they are assigned to the $tasks variable
Make sure your $sync array values and $task['sync'] are integer types and not strings or the '<=' comparison may have unexpected results
I don't know where $time gets its value from based on code I see so verify that it does actually have a value when you try to set it
A good first step when debugging is to try to isolate the problem's location first and then worry about the cause. Using something like var_dump to verify that values of certain variables are as expected at various locations in your script is very useful. Once you know where things start going wrong you can focus your attention in the right place to find out why and come up with a solution. I recommend doing this and letting us know what you find.

Answer 2

I solved my question.
Which was if this is allowed, I tested and it is.
$ar=array('1'=>'a','2'=>'b','3'=>'c');
$index=2;
echo $ar[$index];