Use this code to search for a record, then grab the record ID

Filemaker PHP - Find EXACT Record for Editing

<?php
include ("/www/htdocs/fmphp/access.php");


$find = $fm->newFindCommand('Table');

// use == for an exact search!
$find->addFindCriterion('id',"==". $_POST['id']);
$find->addFindCriterion('student_id',"==". $_POST['student_id']);
$result = $find->execute();

// check for errors

$error = Filemaker::isError($result);

if (!$error) {
  $records = $result->getRecords();
  // grab the record id for the found record
  $recID = $records[0]->getRecordId();
}

?>