Twilio - Unable to get client id while making call - php

Question

I am getting an error "Unable to get Client ID" while initiating the call from Twilio API via JavaScript SDK.
Here is the PHP Code
$callerId = "+1xxxxxxxxxx";
if (isset($_REQUEST['PhoneNumber'])) {
$number = htmlspecialchars($_REQUEST['PhoneNumber']);
}
if (preg_match("/^[\d\+\-\(\) ]+$/", $number)) {
$numberOrClient = "<Number>" . $number . "</Number>";
} else {
$numberOrClient = "<Client>" . $number . "</Client>";
}
$xml = '<Response>
<Dial callerId="'.$callerId.'">
'.$numberOrClient.'
</Dial>
<Record timeout="1000" transcribe="true" />
</Response>';
Here is the error screenshot

Answer 1

It seems $number is an empty string when you call the function and this produces invalid TwiML.
According to the documentation, the <Client> tag needs to contain a string or several tags to specify the clientId.
<?xml version="1.0" encoding="UTF-8"?>
<Response>
<Dial>
<Client>
<Identity>user_jane</Identity>
<Parameter name="FirstName" value ="Jane"/>
<Parameter name="LastName" value ="Doe" />
</Client>
</Dial>
</Response>
or
<?xml version="1.0" encoding="UTF-8"?>
<Response>
<Dial>
<Client>joey</Client>
</Dial>
</Response>