How can I subtract 3 days from a date?

Question

I have a sync script that syncs domain expiration dates with next due date for billing. Right now the script works great if you want the expiration date to equal the next due date.

But I need the next due date to be three days before the expiration, so I need the code to subtract 3 days from the $expirydate in the following code snippet (Full script code is below):

if ($SyncNextDueDate) {
update_query ( "tbldomains", array ("nextduedate" => $expirydate ), array ("domain" => $domainname ) );
}

Full code:

<?php

require dirname ( __FILE__ ) . '/../../../dbconnect.php';
require ROOTDIR . '/includes/functions.php';
require ROOTDIR . '/includes/registrarfunctions.php';

$cronreport = 'Internet.bs Domain Sync Report<br>
---------------------------------------------------<br>
';
/**
* gets expiration date from domain list command
* @param string $data - command TEXT response
* @return array - associative array having as key the domain name and as value the expiration date
*/
function parseResult($data) {
$result = array ();
$data=strtolower($data);
$arr = explode ( "\n", $data );
$totalDomains = 0;
$assocArr = array ();
foreach ( $arr as $str ) {
    list ( $varName, $value ) = explode ( "=", $str );
    $varName = trim ( $varName );
    $value = trim ( $value );
    if ($varName == "domaincount") {
        $totalDomains = intval ( $value );
    }
    $assocArr [$varName] = $value;

}
if ($assocArr ["status"] != "success") { 
    return false;   
}

for($i = 0; $i < $totalDomains; $i ++) {
    list ( $y, $m, $d ) = explode ( "/", $assocArr ["domain_" . $i . "_expiration"] );
    $status = strtolower ( $assocArr ["domain_" . $i . "_status"] );
            if(!is_numeric($y) || !is_numeric($m) || !is_numeric($d)){
                $ddat = array ("expiry" => null, "status" => $status );
            } else {
                $ddat = array ("expiry" => mktime ( 0, 0, 0, $m, $d, $y ), "status" => $status );
            }
    $result [strtolower ( $assocArr ["domain_" . $i . "_name"] )] = $ddat;
    if (isset ( $assocArr ["domain_" . $i . "_punycode"] )) {
        $result [strtolower ( $assocArr ["domain_" . $i . "_punycode"] )] = $ddat;
    }
}
return $result;
}

$params = getregistrarconfigoptions ( 'internetbs' );

$postfields = array ();
$postfields ['ApiKey'] = $params ['Username'];
$postfields ['Password'] = $params ['Password'];
$postfields ['ResponseFormat'] = 'TEXT';
$postfields ['CompactList'] = 'no';
$testMode = trim(strtolower($params ['TestMode']))==="on";
$SyncNextDueDate = trim(strtolower($params ["SyncNextDueDate"]))==="on";

if ($testMode) {
$url = 'https://testapi.internet.bs/domain/list';
} else {
$url = 'https://api.internet.bs/domain/list';
}

$ch = curl_init ();
curl_setopt ( $ch, CURLOPT_URL, $url );

curl_setopt ( $ch, CURLOPT_SSL_VERIFYPEER, FALSE );
curl_setopt ( $ch, CURLOPT_SSL_VERIFYHOST, 0 );

curl_setopt ( $ch, CURLOPT_HEADER, 0 );
curl_setopt ( $ch, CURLOPT_USERAGENT, "WHMCS Internet.bs Corp. Expiry Sync Robot" );
curl_setopt ( $ch, CURLOPT_RETURNTRANSFER, 1 );
curl_setopt ( $ch, CURLOPT_POST, 1 );
curl_setopt ( $ch, CURLOPT_POSTFIELDS, $postfields );

$data = curl_exec ( $ch );
$curl_err = false;


  if (curl_error ( $ch )) {
    $curl_err = 'CURL Error: ' . curl_errno ( $ch ) . ' - ' . curl_error ( $ch );
    exit ( 'CURL Error: ' . curl_errno ( $ch ) . ' - ' . curl_error ( $ch ) );
    }
    curl_close ( $ch );
    if ($curl_err) {
        $cronreport .= "Error connecting to API: $curl_err";
    } else {

    $result = parseResult ( $data );
    if (! $result) {
        $cronreport .= "Error connecting to API:<br>" . nl2br ( $data ) . "<br>";
    } else {
        $queryresult = select_query ( "tbldomains", "domain", "registrar='internetbs' AND (status='Pending Transfer' OR status='Active')" );
        while ( $data = mysql_fetch_array ( $queryresult ) ) {
            $domainname = trim ( strtolower ( $data ['domain'] ) );
            if (isset ( $result [$domainname] )) {
                                if(!is_null($result [$domainname] ["expiry"])){
                                    $expirydate = date ( "Y-m-d", $result [$domainname] ["expiry"] );
                                } else {
                                    $expirydate = false;
                                }
                $status = $result [$domainname] ["status"];
                if ($status == 'ok') {
                    update_query ( "tbldomains", array ("status" => "Active" ), array ("domain" => $domainname ) );
                }
                if ($expirydate) {
                    update_query ( "tbldomains", array ("expirydate" => $expirydate ), array ("domain" => $domainname ) );
                    if ($SyncNextDueDate) {
                        update_query ( "tbldomains", array ("nextduedate" => $expirydate ), array ("domain" => $domainname ) );
                    }
                    $cronreport .= '' . 'Updated ' . $domainname . ' expiry to ' . frommysqldate ( $expirydate ) . '<br>';
                }
            } else {
                $cronreport .= '' . 'ERROR: ' . $domainname . ' -  Domain does not appear in the account at Internet.bs.<br>';
            }
        }
    }
}
logactivity ( 'Internet.bs Domain Sync Run' );
sendadminnotification ( 'system', 'WHMCS Internet.bs Domain Syncronisation Report', $cronreport );

?>

Answer 1

$date = new DateTime($expirydate);
$date->sub(new DateInterval('P3D');
$expirydate = $date->format('Y-m-d');

or as a one-liner:

$expirydate = (new DateTime($expirydate))->sub(new DateInterval('P3D'))->format('Y-m-d');

Here's a slightly different method:

$date = new DateTime($expirydate);
$date->modify('-3 days');
$expirydate = $date->format('Y-m-d');