<?php
// $a heeft de json in zich
$a = '{"champions":[{"id":266,"name":"Aatrox","active":true,"attackRank":8,"defenseRank":4,"magicRank":3,"difficultyRank":6,"botEnabled":false,"freeToPlay":false,"botMmEnabled":false,"rankedPlayEnabled":true},
{"id":103,"name":"Ahri","active":true,"attackRank":3,"defenseRank":4,"magicRank":8,"difficultyRank":8,"botEnabled":false,"freeToPlay":false,"botMmEnabled":false,"rankedPlayEnabled":true},
{"id":84,"name":"Akali","active":true,"attackRank":5,"defenseRank":3,"magicRank":8,"difficultyRank":6,"botEnabled":false,"freeToPlay":false,"botMmEnabled":false,"rankedPlayEnabled":true}]}';
// zet de json om naar een PHP object
$obj = json_decode($a);
// dump het complete object op het scherm om te lezen hoe het is opgebouwd
echo '<pre>';
print_r($obj);
echo '</pre>';