Best way to use multiple nested loops - php

Question

I am using php for this, but answers that are not language specific are also welcome.
I have several arrays of objects that I want to loop through and output in order. Each of the arrays have a different kind of object in them, but all of the objects have a unique order attribute.
For example:
$people = [{'name':'George','email':'George#test.com','order':'2'},{'name...];
$sandwiches = [{'type':'bacon','rating':'8/10','order':'1'},{'type...];
$restaurants = ....
$chefs = ...
...
What is the most efficient way to loop through them in order?
Assuming I can determine the maximum order I figured I could do something like:
for($i=0; $i< $maximumOrder; $i++)
{
for($j=0; $j< count($people); $j++)
{
if($people[$j]->order == $i)
{
//Do the things I want to do
break;
}
}
for($j=0; $j< count($sandwiches); $j++)
{
if($sandwiches[$j]->order == $i)
{
//Do the things I want to do
break;
}
}
for($j=0; $j< count($restaurants); $j++)
{
.....
}
But this isn't very good because even if the item with the desired order is found in people it will still continue looping through all the other arrays. I could just add a Boolean variable to show if the desired item has already been found (see below), but I am sure there are better ways to do this.
for($i=0; $i< $maximumOrder; $i++)
{
$found = false;
for($j=0; $j< count($people); $j++)
{
if($people[$j]->order == $i)
{
//Do the things I want to do
$found = true;
break;
}
}
if(!$found == true)
{
for($j=0; $j< count($sandwiches); $j++)
{
if($sandwiches[$j]->order == $i)
{
//Do the things I want to do
$found = true;
break;
}
}
}
if(!$found == true)
{
for($j=0; $j< count($restaurants); $j++)
{
.....
}
The below is based on #Victory's answer, with the addition of an elseif statement, to stop the while loop if it goes passed the desired order number (given these are now sorted arrays). This I believe should increase efficiency (at least with big arrays), but please correct me if I am wrong?
function orderArrayByOrder($a,$b)
{
return ($a->order < $b->order) ? -1 : 1;
}
$a1 = usort($people, "orderArrayByOrder");
$a2 = usort($sandwiches, "orderArrayByOrder");
$a3 = usort($restaurants, "orderArrayByOrder");
$c1 = count($a1)
$c2 = count($c2)
$c3 = count($c3)
$i1 = 0
$i2 = 0
$i3 = 0
// itertor over order
for ($curOrder ... $maxorder)
{
while ($i1 < $c1)
{
if($a1[$i1]->order == $curOrder)
{
//Do what I need to do
break;
}
elseif($a1[$i1]->order > $curOrder)
{
//We know the order won't exist in this array.
break;
}
$i1++;
}
while ($i2 < $c2)
{
if($a2[$i2]->order == $curOrder)
{
//Do what I need to do
break;
}
elseif($a2[$i2]->order > $curOrder)
{
break;
}
$i1++;
}
}

Answer 1

Basically you need to sort each array and find the maxorder, then you loop over the order index and print the items with the given order. This is O(N Log(N)) because of the sorting where N = max number of elements
Here is some pseudo code
sort each array (in php use usort) - O(N log(N))
find maxorder (iterate over each) - O(N)
create an array each index
get the length of each index and store
$a1 = usort($people, function(){})
$a2 = usort($places, function(){})
$a3 = usort($things, function(){})
$c1 = count($a1)
$c2 = count($c2)
$c3 = count($c3)
$i1 = 0
$i2 = 0
$i3 = 0
// itertor over order
for ($curOrder ... $maxorder) {
// while $a1 is on current order and its index is in bound
while ($i1 < $c1 && $a1[$i1]->order == $curOrder) {
echo $a1[$i1]->value;
$i1++;
}
while ($i2 < $c2 && $a2->order == $curOrder) {
echo $a2[$i2]->value;
$i2++;
}
while ($i3 < $c3 && $a3->order == $curOrder) {
echo $a3[$i3]->value;
$i3++;
}
}

Answer 2

If you reindex each array by the object's order value, then you can retrieve an object with a given order in constant time. The code retrieves all related objects in O(n) because you're looking at each element a constant number of times (notice the nested loops have been removed).
$peopleByOrder = array();
$sandwichesByOrder = array();
$restaurantsByOrder = array();
$uniqueOrderKeys = array();
foreach($people as $person) {
$peopleByOrder[$person->order] = $person;
$uniqueOrderKeys[$person->order] = 1;
}
// same for $sandwichesByOrder and $restaurantsByOrder
foreach(array_keys($uniqueOrderKeys) as $oderKey) {
if(isset($peopleByOrder[$orderKey])) {
$person = $peopleByOrder[$orderKey];
}
else if(isset($sandwichesByOrder[$orderKey])) {
$sandwich = $sandwichesByOrder[$orderKey];
}
else if(isset($restaurantsByOrder[$orderKey])) {
$restaurant = $restaurantsByOrder[$orderKey];
}
}