curl.sh

curl 'https://free.navalny.com/api/v1/maps/counters/' --silent \
   -H 'authority: free.navalny.com' \
   -H 'sec-ch-ua: "Chromium";v="88", "Google Chrome";v="88", ";Not A Brand";v="99"' \
   -H 'accept: application/json' \
   -H 'sec-ch-ua-mobile: ?0' \
   -H 'user-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/88.0.4324.96 Safari/537.36' \
   -H 'content-type: application/json' \
   -H 'sec-fetch-site: same-origin' \
   -H 'sec-fetch-mode: cors' \
   -H 'sec-fetch-dest: empty' \
   -H 'referer: https://free.navalny.com/' \
   -H 'accept-language: en-AU,en;q=0.9,ru;q=0.8,en-US;q=0.7' \
   -H 'cookie: __cfduid=da40ec8546392d5d2a7eeb703381d4c061616510304; _gid=GA1.2.323931406.1616510307; _gat_gtag_UA_37043611_61=1; _ga=GA1.2.1493947144.1616510306; _ga_QT5M43QH13=GS1.1.1616510306.1.1.1616510513.0' \
   --compressed

loop.php

<?php

while(true) {
    // sleeping till the second start
    $mic = 1 - explode(" ", microtime())[0];
    usleep($mic * 1e6);

    $executed = shell_exec("./curl.sh | grep persons");
    $result = json_decode(trim($executed));
    echo date("d.m.Y H:i:s") . "\t" . $result->persons . "\n";
}