Checking game objects versus each other to determine targets, comparing arrays

I have a flight class that looks like this:

class Flight {
 public $id; // unique id
 public $structures = array(); // each "structure" indicates one fighter class assembled in this flight class
 public $dogfights = array() if the flight is dogfighting, this array holds the ID of each opposing flight we are dogfighting
}

class Fighter { // this is whats inside $Flight->structures
 public $id
 public $parentid 
}

If two opposing flights are close to each other, I initiate a dogfight. I determine if they are dogfighting like this:

public function initiateDogfights(){
    $dogfights = array();

    for ($i = 0; $i ships)-1; $i++){
        for ($j = $i+1; $j ships); $j++){
            $dist = Math::getDist2($this->ships[$i]->getCurrentPosition(), $this->ships[$j]->getCurrentPosition());
            if ($dist ships[$i]->size / 2 + $this->ships[$j]->size / 2){
                $new = true;
                for ($k = 0; $k ships[$i]->dogfights); $k++){
                    if ($this->ships[$i]->dogfights[$k] == $this->ships[$j]->id){
                        $new = false;
                    }
                }
                if ($new){
                    $this->ships[$i]->dogfights[] = $this->ships[$j]->id;
                    $this->ships[$j]->dogfights[] = $this->ships[$i]->id;
                    $dogfights[] = array(0 => $this->ships[$i]->id, 1 => $this->ships[$j]->id);
                }
            }
        }
    }
    if (sizeof($dogfights)){
        DBManager::app()->insertDogfights($this->gameid, $this->turn, $dogfights);
    }
}

Basicly, I compare all ships versus all ships (aka flights), compare their distance to each other. If it's below a threshold, I push the opposing flights ID into the flights->dogfights array.

I check if the dogfights are new, because they might have been transferred from the DB and alas be initiated a turn ago. So, each flight's $dogfights prop holds the IDs of all opposing flights this flight is tackling. Now, this

I agree with Mike Brant's comments that it would be better to have the complete code posted for a broad review but that likely won't happen- if you do want to do so then I advise you to do so in a new post, since editing your post might invalidate the advice below. Nonetheless i see a few idiomatic PHP aspects that could be improved.

The code could be simplified using PHP’s foreach loops instead of for loops- e.g.

for ($i = 0; $i ships)-1; $i++){
    for ($j = $i+1; $j ships); $j++){

this could be simplified using foreach loops with the range() function:

foreach (range(0, sizeof($this->ships)-2) as $i) {
    foreach (range($i, sizeof($this->ships)-1) as $j) {

and also the loop in createFireOrders():

for ($i = 0; $i structures); $i++){
        if (!$this->structures[$i]->destroyed){

with foreach there is no need to do the bookkeeping on the counter variable:

foreach ($this->structures as $i => $structure) {

and instead of referring to $this->structures[$i] just use $structure.

The array on this line in initiateDogfights():

$dogfights[] = array(0 => $this->ships[$i]->id, 1 => $this->ships[$j]->id);

doesn't need to have the indexes explicitly set:

$dogfights[] = array($this->ships[$i]->id, $this->ships[$j]->id);

StackExchange Code Review Q#155541, answer score: 4