pagerduty "who's on-call" for slack

index.php

<?php
if ( $_POST["token"] != "REDACTED" ) {
        header("HTTP/1.1 403 Forbidden");
        die();
}

$SLACK_TEXT = preg_replace ( "/$_POST[trigger_word]/", '', $_POST[text] );


function whos_on_call ( $when ) {
        $PD_API_TOKEN = 'REDACTED';
        $SINCE = date( "Y-m-d", strtotime( $when ) ) ."T20:00:00.0600" ;
        $UNTIL = date ( "Y-m-d", strtotime( $when ." +1 day" ) );
        //return "since: ". $SINCE . ".... until: ". $UNTIL;
        $ON_CALL_PRIMARY = json_decode ( exec ( "curl --get --header 'Authorization: Token token=$PD_API_TOKEN' --header 'Accept: application/vnd.pagerduty+json;version=2' \"https://api.pagerduty.com/schedules/REDACTED/users/?since=$SINCE&until=$UNTIL\" 2>/dev/null "), true);
        $ON_CALL_SECONDARY = json_decode ( exec ( "curl --get --header 'Authorization: Token token=$PD_API_TOKEN' --header 'Accept: application/vnd.pagerduty+json;version=2' \"https://api.pagerduty.com/schedules/REDACTED/users/?since=$SINCE&until=$UNTIL\" 2>/dev/null "), true);
        //print_r($ON_CALL);
        //die();
        return $ON_CALL_PRIMARY['users']['0']['name']." is primary on-call.  ". $ON_CALL_SECONDARY['users']['0']['name'] ." is secondary.";
}

if ( preg_match ( '/(on call)|(oncall)/i', $SLACK_TEXT ) ) {
        $WHEN = ( preg_replace ( "/ ((on call)|(oncall))/i", '', $SLACK_TEXT ) ) ?: "today";
        $SLACK_RESPONSE = whos_on_call ( $WHEN );
} else {
        $SLACK_RESPONSE = "Possible commands:
oncall [when] .................... Show who is on call per PagerDuty";
}

?>

{
    "attachments": [
        {
            "text": "```<?php print $SLACK_RESPONSE; ?>```",
            "mrkdwn_in": [
                "text"
            ]
        }
    ]
}