sample.php

public function textToSpeech($text)
{
	$file = md5($text) . '.mp3';
	$file_path = __DIR__ . '/audio/' . $file;

	if (!file_exists($file_path)) {
		$textToSpeechClient = new TextToSpeechClient([
			'credentials' => ''
		]);
		$input = (new SynthesisInput())
			->setSsml($text);

		$voice = (new VoiceSelectionParams())
			->setLanguageCode('en-US')
			->setName('en-US-Wavenet-B')
			->setSsmlGender(SsmlVoiceGender::MALE);

		$audioConfig = (new AudioConfig())
			->setAudioEncoding(AudioEncoding::MP3);

		$resp = $textToSpeechClient->synthesizeSpeech($input, $voice, $audioConfig);

		file_put_contents($file_path, $resp->getAudioContent());
	}

	return $file;
}