In reply to performance tests array_unique vs foreach.
In PHP7 there were significant changes to Packed and Immutable arrays resulting in the performance difference to drop considerably. Here is the same test on php7.1 here;
http://sandbox.onlinephpfunctions.com/code/2a9e986690ef8505490489581c1c0e70f20d26d1
$max = 770000; //large enough number within memory allocation
$arr = range(1,$max,3);
$arr2 = range(1,$max,2);
$arr = array_merge($arr,$arr2);
$time = -microtime(true);
$res1 = array_unique($arr);
$time += microtime(true);
echo "deduped to ".count($res1)." in ".$time;
// deduped to 513333 in 1.0876770019531
$time = -microtime(true);
$res2 = array();
foreach($arr as $key=>$val) {
$res2[$val] = true;
}
$res2 = array_keys($res2);
$time += microtime(true);
echo "<br />deduped to ".count($res2)." in ".$time;
// deduped to 513333 in 0.054931879043579