text to speect AZURE add silence - php

Question

Hi I'm trying to add a pause in the text to speech Azure api, this code works fine but I can't add silence. I need to add silence when a specific character is found in the text, I tried with or <mstts:ttsbreak strength="none" /> but the audio output speech the tags instead to make a pause.
$doc = new DOMDocument();
$root = $doc->createElement( "speak" );
$root->setAttribute( "xmlns" , "http://www.w3.org/2001/10/synthesis" );
$root->setAttribute( "xmlns:mstts" , "http://www.w3.org/2001/mstts" );
$root->setAttribute( "xmlns:emo" , "http://www.w3.org/2009/10/emotionml" );
$root->setAttribute( "version" , "1.0" );
$root->setAttribute( "xml:lang" , "$spechlang" );
$voice = $doc->createElement( "voice" );
$voice->setAttribute( "name" , "$myvoice");
$style = $doc->createElement( "mstts:express-as" );
$style->setAttribute( "style" , "whispering"); //
$prosody = $doc->createElement( "prosody" );
$prosody->setAttribute( "rate" , "$rate.00%" );
$prosody->setAttribute( "pitch" , "$pitch.00%" );
$text = $doc->createTextNode( "$mytext" );
$prosody->appendChild( $text );
$style->appendChild( $prosody );
$voice->appendChild( $style );
$root->appendChild( $voice );
$doc->appendChild( $root );
$data = $doc->saveXML();
$options = array(
'http' => array(
'header' => "Content-type: application/ssml+xml\r\n" .
"X-Microsoft-OutputFormat: riff-24khz-16bit-mono-pcm\r\n" .
"Authorization: "."Bearer ".$access_token."\r\n" .
"X-Search-AppId: 07D3234E56TT426DAA29772419F436CA\r\n" .
"X-Search-ClientID: 1ECFAE91406677A480F00935DC390960\r\n" .
"User-Agent: TTSPHP\r\n" .
"content-length: ".strlen($data)."\r\n",
'method' => 'POST',
'content' => $data,
),
);
$context = stream_context_create($options);
// get the wave data
$result = file_get_contents($ttsServiceUri, false, $context);
a ssml generated could be
<speak xmlns="http://www.w3.org/2001/10/synthesis" xmlns:mstts="http://www.w3.org/2001/mstts" xmlns:emo="http://www.w3.org/2009/10/emotionml" version="1.0" xml:lang="it-IT">
<voice name="en-US-JennyNeural">
1. first point: <break strength="medium" />
lore lipso bla bla.
</voice></speak>
this SSML work fine on https://speech.microsoft.com/portal SPEECH STUDIO PORTAL but not in my php. thanks