Sort Concerts

<?php
    $input = ["ZZ Top | London | 2-Aug-2014 | Wembley Stadium",
    "Iron Maiden | London | 28-Jul-2014 | Wembley Stadium",
    "Metallica | Sofia | 11-Aug-2014 | Lokomotiv Stadium",
    "Helloween | Sofia | 1-Nov-2014 | Vassil Levski Stadium",
    "Iron Maiden | Sofia | 20-June-2015 | Vassil Levski Stadium",
    "Helloween | Sofia | 30-July-2015 | Vassil Levski Stadium",
    "Iron Maiden | Sofia | 26-Sep-2014 | Lokomotiv Stadium",
    "Helloween | London | 28-Jul-2014 | Wembley Stadium",
    "Twisted Sister | London | 30-Sep-2014 | Wembley Stadium",
    "Metallica | London | 03-Oct-2014 | Olympic Stadium",
    "Iron Maiden | Sofia | 11-Apr-2016 | Lokomotiv Stadium",
    "Iron Maiden | Buenos Aires | 03-Mar-2014 | River Plate Stadium"];

    $concerts = [];

    for ($i=0; $i < count($input); $i++) {
        $row = explode(" | ", $input[$i]);
        for ($j=0; $j < count($row); $j++) {
            if (isset($concerts[$row[1]])) {
                if (isset($concerts[$row[1]][$row[3]])) {
                    if (in_array($row[0], $concerts[$row[1]][$row[3]])) {
                        continue;
                    }
                    else {
                        array_push($concerts[$row[1]][$row[3]], $row[0]);
                    }
                }
                else {
                    $concerts[$row[1]][$row[3]] = [];
                    array_push($concerts[$row[1]][$row[3]], $row[0]);
                }
            }
            else {
                $concerts[$row[1]] = [];
                $concerts[$row[1]][$row[3]] = [];
                array_push($concerts[$row[1]][$row[3]], $row[0]);
            }
        }
    }
    ksort($concerts);
    foreach ($concerts as $key => $value) {
        ksort($concerts[$key]);
        foreach ($concerts[$key] as $inner => $value) {
            sort($concerts[$key][$inner]);
        }
    }
    echo json_encode($concerts);
?>