gistfile1.php

$apiKey = "aaaaaaaaaaaaaaaaaaaa"; // Replace with real api key
$summonerName = $_GET['nick1'];
$apiUrl = "http://api.elophant.com/v2/euw/summoner/{$summonerName}?key={$apiKey}";
$jsonObject = json_decode(file_get_contents($apiUrl));
 
if ( isset($jsonObject['data']) ) {
  $data = $jsonObject->{'data'};
 
  if ( isset($data['summonerId']) ) {
    $summonerId = $data->{'summonerId'};
    
    if ( $summonerId == $_GET['steamid1']) {
      // The id matches the one the user provided.. Horay!
    } else {
      // Tell the user that he entered an invalid summoner id
    }
  } else {
    // Tell the user that the summoner does not exist
  }
} else {
  // Tell the user that the summoner does not exist
}