Another way could be to have a mini-form, with the form’s action attribute set to your form page, and with a hidden input containing the job number (using the TV). Then you could use this snippet on your eform page...
if(isset($_POST['jobnum']) && is_numeric($_POST['jobnum'])) { // minimal input validation
$modx->setPlaceholder('JobNumber', $_POST['jobnum']);
}
return;
Then in your eForm template you could use [+JobNumber+] wherever you wanted to use the job number. Just make sure your snippet is inserted before the eForm snippet.
In PHP, POST values are always strings, so the
is_numeric check is used; if you’re using some other form of job identifier (mixed alphanumeric, for example) then some other sanity check would be needed.