<?php //php 7.2.24

$json = '{"response":{"count":10,"items":[{"id":76,"from_id":-206341834,"owner_id":-206341834,"date":1635582068,"marked_as_ads":0,"post_type":"post","text":"","attachments":[{"type":"photo","photo":{"album_id":-7,"date":1635582068,"id":457239054,"owner_id":-206341834,"has_tags":false,"access_key":"76e2c3a835f5a4cc1d","post_id":76,"sizes":[{"height":21,"url":"https:\/\/sun9-41.userapi.com\/impg\/Jl2qOYk10GNB5SfzzpiHksZYSC4rw9sQRR7oFA\/TVvXcAsnENA.jpg?size=75x21&quality=96&sign=8aa84cb6975e4de920245e769cf2a53f&c_uniq_tag=sLINAUcU8unP7Fy0u6LVFVW6okvRhFVqd0pvQDOLMCQ&type=album","type":"s","width":75},{"height":37,"url":"https:\/\/sun9-41.userapi.com\/impg\/Jl2qOYk10GNB5SfzzpiHksZYSC4rw9sQRR7oFA\/TVvXcAsnENA.jpg?size=130x37&quality=96&sign=85670086f0d1fc48cebffb19fd6051f8&c_uniq_tag=aqj7l9zkLyurmUipyH7hnOQa--cgtKEpPCfAZLoAT7g&type=album","type":"m","width":130},{"height":172,"url":"https:\/\/sun9-41.userapi.com\/impg\/Jl2qOYk10GNB5SfzzpiHksZYSC4rw9sQRR7oFA\/TVvXcAsnENA.jpg?size=604x172&quality=96&sign=411f8b44e840be3e3fab13f8a571e573&c_uniq_tag=n7WU0f_Z0U2l5vQcZ_oJvCjl_dylcHdtp27_skvzOM4&type=album","type":"x","width":604},{"height":230,"url":"https:\/\/sun9-41.userapi.com\/impg\/Jl2qOYk10GNB5SfzzpiHksZYSC4rw9sQRR7oFA\/TVvXcAsnENA.jpg?size=807x230&quality=96&sign=4f7adb4ccbc1356e93242b37bee5f3d8&c_uniq_tag=Mom16YuevSy4N3BUQjpWWP_rxgd8_GoK04x5DDCsdfg&type=album","type":"y","width":807},{"height":286,"url":"https:\/\/sun9-41.userapi.com\/impg\/Jl2qOYk10GNB5SfzzpiHksZYSC4rw9sQRR7oFA\/TVvXcAsnENA.jpg?size=1004x286&quality=96&sign=6294e717d879a6c6817ffa63cc88a2c0&c_uniq_tag=RjM7SnmnqAmOhbaSMGlyuejYT57m8qiuSN4Dlh6zpmU&type=album","type":"z","width":1004},{"height":87,"url":"https:\/\/sun9-41.userapi.com\/impg\/Jl2qOYk10GNB5SfzzpiHksZYSC4rw9sQRR7oFA\/TVvXcAsnENA.jpg?size=130x87&quality=96&crop=288,0,427,286&sign=597fc3aa018be2fe2ec5d4a9ac0451fd&c_uniq_tag=T-CKMuVm406BtIZw98ZJ_NxkdoupFQMqRCa1V7drcE4&type=album","type":"o","width":130},{"height":133,"url":"https:\/\/sun9-41.userapi.com\/impg\/Jl2qOYk10GNB5SfzzpiHksZYSC4rw9sQRR7oFA\/TVvXcAsnENA.jpg?size=200x133&quality=96&crop=287,0,430,286&sign=6188ec41453036d893de32ccf7141cf4&c_uniq_tag=t68y12R5nhRVKPoJrPgpReIZZF0j17v9Y1yUqxe6fUk&type=album","type":"p","width":200},{"height":213,"url":"https:\/\/sun9-41.userapi.com\/impg\/Jl2qOYk10GNB5SfzzpiHksZYSC4rw9sQRR7oFA\/TVvXcAsnENA.jpg?size=320x213&quality=96&crop=287,0,430,286&sign=7b203f726f6166072fa985d75b30a86e&c_uniq_tag=fYQ_zJaFaJLw2QQu1WzvZkpXZ9DABoEZR9rk12wmV-4&type=album","type":"q","width":320},{"height":286,"url":"https:\/\/sun9-41.userapi.com\/impg\/Jl2qOYk10GNB5SfzzpiHksZYSC4rw9sQRR7oFA\/TVvXcAsnENA.jpg?size=510x286&quality=96&crop=247,0,510,286&sign=73773ebeaa1b32614f363e09077d49e6&c_uniq_tag=OVXA90aetOhzt8HzcwRD95eRbUPUwNvK75VG2_ENqWY&type=album","type":"r","width":510}],"text":"","user_id":100}}],"post_source":{"type":"vk"},"comments":{"can_post":1,"count":0,"groups_can_post":true},"likes":{"can_like":1,"count":0,"user_likes":0,"can_publish":1},"reposts":{"count":0,"user_reposted":0},"donut":{"is_donut":false},"short_text_rate":0.800000,"hash":"80fJag8LLqgU0VXNjw"}]}}';

$data = json_decode($json);

$sizes = $data->response->items[0]->attachments[0]->photo->sizes;
    
    foreach ($sizes as $size){
        if($size->width === 604){
            $url = $size->url;
            break;
        }
    }

    echo $url ?? null
?>