Obtención automática de enlace MP4 de Xvideos

<?php

// register shortcode
add_shortcode('devuelveflv', 'PHP_Devuelve_Flv');

// include PHP file
// Devuelve una cadena entre dos tags
function get_string_between($string, $start, $end){
    $string = " ".$string;
    $ini = strpos($string,$start);
    if ($ini == 0) return "";
    $ini += strlen($start);
    $len = strpos($string,$end,$ini) - $ini;
return substr($string,$ini,$len);
}

function PHP_Devuelve_Flv($params=array()) {

    extract(shortcode_atts(array(
        'urlorigen' => 'default'
    ), $params));

    $ch = curl_init();
    // $urlorigen-ejemplo: "http://www.xvideos.com/video259513/black_girl_with_perfect_big_boobs_training"
    curl_setopt($ch, CURLOPT_URL, $urlorigen);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    $output = curl_exec($ch);
    curl_close($ch);
    $urlflv = get_string_between($output, "flv_url=", "url_bigthumb");
    if ($urlflv<>'') {
        // The payment is valid

        $urlflv=rawurldecode($urlflv);
        //echo do_shortcode('[fvplayer src="' . $urlflv . '" width="510" height="400"]');
                echo do_shortcode('[fvplayer src="' . $urlflv.'"]');
    }
    else {
        // El video no está disponible
        echo '<H2>Sorry, Video not available</H2>';
    }
    
}

<?php

// register shortcode
add_shortcode('devuelveflv', 'PHP_Devuelve_Flv');

function get_string_between($string, $start, $end){
    $string = " ".$string;
    $ini = strpos($string,$start);
    if ($ini == 0) return "";
    $ini += strlen($start);
    $len = strpos($string,$end,$ini) - $ini;
return substr($string,$ini,$len);
}

function PHP_Devuelve_Flv($params=array()) {

    extract(shortcode_atts(array(
        'urlorigen' => 'default'
    ), $params));

    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $urlorigen);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_USERAGENT, "Mozilla/5.0 (Linux; U; Android 4.0; en-us; GT-I9300 Build/IMM76D)");

    $output = curl_exec($ch);
    curl_close($ch);
    
    preg_match("/mobileReplacePlayerDivTwoQual(.*)<\/script>/i", $urlorigen, $maturl);
    $urlflv = get_string_between($output, "mp4", "url_bigthumb");
    
    if ($urlflv<>'') {
        $urlflv=rawurldecode($urlflv);
                echo do_shortcode('[fvplayer src="' . $urlflv.'"]');
    }
    else {
        echo '<H2>Error. El video no se encuentra disponible en Xvideos o Redtube</H2>';
    }
    
}