My telegram bot sends message again and again while I will start sending message to members, if members' count more than 500.

I am using this code for sending message:

<?php
define('API_KEY',"[*API_TOKEN*]");
function bot($method,$datas=[]){
    $url = "https://api.telegram.org/bot".API_KEY."/".$method;
    $ch = curl_init();
    curl_setopt($ch,CURLOPT_URL,$url);
    curl_setopt($ch,CURLOPT_RETURNTRANSFER,true);
    curl_setopt($ch,CURLOPT_POSTFIELDS,$datas);
    $res = curl_exec($ch);
    if(curl_error($ch)){
        var_dump(curl_error($ch));
    }else{
        return json_decode($res);
    }
}
}

$member = file_get_contents("members.json");
$js = json_decode($member);
if(is_object($js)){
    $js = get_object_vars($js);
}
foreach($js as $mem){
    bot('sendMessage',[
        'chat_id'=>$mem,
        'text'=>"Message text to send"
    ]);
}
?>

How I can fix this bug?