Fixing eForm onMailSent Callback Errors

eForm callback hooks are useful, but they are also easy to misconfigure. The classic failure looks like this:

Fatal error: Call to undefined function 'mailSent'()

Typical Setup

[[eForm?
 &eFormOnMailSent=`mailSent`
 ...
]]

function mailSent(&$fields) {
    global $modx;
    $modx->setPlaceholder('schet', '1234');
    return true;
}

What to Check

• whether the callback function is loaded before eForm tries to call it
• whether quotes, parameter names, or snippet wrappers are malformed
• whether the hook lives in the correct execution context

In callback-based setups, a working function body is not enough. The CMS also needs to know about that function at the exact moment the hook fires.