PHP Wait before sending next api request - php

Question

I have a website that pulls prices from an API. The problem is that if you send more than ~10 requests to this API in a short amount of time, your ip gets blocked temporarily (I'm not sure if this is just a problem on localhost or if it would also be a problem from the webserver, I assume the latter).
The request to the API returns a JSON object, which I then parse and store certain parts of it into my database. There are about 300 or so entries in the database, so ~300 requests I need to make to this API.
I will end up having a cron job that every x hours, all of the prices are updated from the API. The job calls a php script I have that does all of the request and db handling.
Is there a way to have the script send the requests over a longer period of time, rather than immediately? The problem I'm running into is that after ~20 or so requests the ip gets blocked, and the next 50 or so requests after that get no data returned.
I looked into sleep(), but read that it will just store the results in a buffer and wait, rather than wait after each request.
Here is the script that the cron job will be calling:
define('HTTP_NOT_FOUND', false);
define('HTTP_TIMEOUT', null);
function http_query($url, $timeout=5000) {
$curl = curl_init($url);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_TIMEOUT_MS, $timeout);
$text = curl_exec($curl);
if($text) {
$code = curl_getinfo($curl, CURLINFO_HTTP_CODE);
switch($code){
case 200:
return $text;
case 404:
return -1;
default:
return -1;
}
}
return HTTP_TIMEOUT;
}
function getPrices($ID) {
$t = time();
$url = url_to_API;
$result = http_query($url, 5000);
if ($result == -1) { return -1; }
else {
return json_decode($result)->price;
}
}
connectToDB();
$result = mysql_query("SELECT * FROM prices") or die(mysql_error());
while ($row = mysql_fetch_array($result)) {
$id = $row['id'];
$updatedPrice = getItemPrices($id);
.
.
echo $updatedPrice;
. // here I am just trying to make sure I can get all ~300 prices without getting any php errors or the request failing (since the ip might be blocked)
.
}

Answer 1

sleep() should not affect/buffer queries to the database. You can use ob_flush() if you need to print something immediately. Also make sure to set max execution time with set_time_limit() so your script don't timeout.
set_time_limit(600);
while ($row = mysql_fetch_array($result)) {
$id = $row['id'];
$updatedPrice = getItemPrices($id);
.
.
echo $updatedPrice;
//Sleep 1 seconds, use ob_flush if necessary
sleep(1);
//You can also use usleep(..) to delay the script in milliseconds
}