for($i = 0; $i <= 100; $i++){
$array[] = rand(-50,50);
}
$hashmap = array();
$pairs = array();
for($i = 0; $i < count($array); $i++){
    $toGiveTen = 10 - $array[$i];
    if(array_key_exists ($toGiveTen, $hashmap)){
        $pairs[] = $hashmap[$toGiveTen] . " + " . $array[$i] . " = 10";
        unset($hashmap[$toGiveTen]);
    } else {
        $hashmap[$array[$i]] = $array[$i];
    }
}
print_r($pairs);