<?php
    $filename = "audio.flac";
    $audio = file_get_contents($filename);
    $data = array(
        "Content_Type"  =>  "audio/x-flac; rate=16000",
        "Content"       =>  $audio,
    );
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, 'https://www.google.com/speech-api/v1/recognize?xjerr=1&client=chromium&lang=en-US');
    curl_setopt( $ch, CURLOPT_HTTPHEADER, array("Content-Type: audio/x-flac; rate=16000"));
    curl_setopt($ch, CURLOPT_POST, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
    ob_start();
    curl_exec($ch);
    curl_close($ch);
    $contents = ob_get_contents();
    ob_end_clean();
    print_e($contents);