Update FileMaker Database API PHP Code to Retrieve Query String

Hello,

I have a little php site created by a wizard software that pulls data out of FileMaker.  I have a current page that currently retrieves the record id out of the url to look up the database record and display the fields from the record.  I want to make a slight modification that will allow me to instead send a PO parameter that would instead look up the record by the PO number instead of the record id when PO=12345 is sent in the query string.  I still want the existing functionality but need to know how to make it either look up record id or po number.  Here is the existing php section that pulls out the record id.

<?php

    /**
    * FileMaker PHP Site Assistant Generated File
    */

    require_once 'fmview.php';
    require_once 'FileMaker.php';
    require_once 'error.php';

    $cgi = new CGI();
    $cgi->storeFile();
   
    $databaseName = 'SalesFM7';
    $layoutName = 'XSLEditLayout';

    $userName = $cgi->get('userName');
    $passWord = $cgi->get('passWord');

    $fm = & new FileMaker();
    $fm->setProperty('database', $databaseName);
    $fm->setProperty('username', $userName);
    $fm->setProperty('password', $passWord);
   
    ExitOnError($fm);
    $layout = $fm->getLayout($layoutName);
    ExitOnError($layout);

    // formats for dates and times
    $displayDateFormat = '%m/%d/%Y';
    $displayTimeFormat = '%I:%M:%S %P';
    $displayDateTimeFormat = '%m/%d/%Y %I:%M:%S %P';
    $submitDateOrder = 'mdy';

    $recid = $cgi->get('-recid');
    if (!isset($recid))
        $recid = 1;
    $record = $fm->getRecordById($layoutName, $recid);
    ExitOnError($record);
   
    class EmptyRecord {
        function getRelatedSet($relationName) {
            return array(new EmptyRecord());
        }

        function getField($field, $repetition = 0) {
        }

        function getRecordId() {
        }
    }
   
?>

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In slight testing on a test page it seems like the following type of code is needed to pull a po number:

$cmd =& $fm->newFindCommand('XSLLayout');
$cmd->addFindCriterion('PO', $_REQUEST['PO']);
$result = $cmd->execute();
if (FileMaker::isError($result)) {
    echo 'unable to find PO: ' . $result->message . '(' . $result->code . ')';
    die();
}
$records = $result->getRecords();

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Does anyone know how to tweak these two pieces of code to work together to make my page a little more dynamic in allowing me either url search?

http://myipaddress/Folder/editrecord.php?PO=12346

or

as is working currently only:

http://myipaddress/Folder/editrecord.php?-action=browse&-recid=5138

Thanks in advance,
Shawn