PHP用于显示来自YouTube网址的视频ID

I am currently trying to retrieve YouTube video IDs through url. I created a function getYoutubeVideoID that strips $url and finds the $sVideoID. The Problem is that when i echo the variable i get an empty value of $sVideoID. How come i am getting no value result for $sVideoID if i am assigning it the video ID?

<?php

if($_POST)
{

$url     = $_POST['yurl'];

function getYoutubeVideoID($url) {
    $sVideoID = preg_replace('~https?://(?:[0-9A-Z-]+\.)?(?:youtu\.be/| youtube\.com\S*[^\w\-\s])([\w\-]{11})      
        (?=[^\w\-]|$)(?![?=&+%\w]*(?:[\'"][^<>]*>| </a>))[?=&+%\w-]*~ix','<a href="http://www.youtube.com/watch?v=$1">YouTube link: $1</a>',$url);
    return $sVideoID;
}

    $hth        = 300; //$_POST['yheight'];
    $wdth       = 500; //$_POST['ywidth'];


?>

<?
//Iframe code

echo htmlentities ('<iframe src="http://www.youtube.com/embed/'.$sVideoID.'" frameborder="0" width="'.$wdth.'" height="'.$hth.'"></iframe>');

?>

<?
//Old way to embed code
echo htmlentities ('<embed src="http://www.youtube.com/v/'.$sVideoID.'" width="'.$wdth.'" height="'.$hth.'" type="application/x-shockwave-flash"  wmode="transparent" embed="" /></embed>');
}
?>

Perhaps I am wrong, or maybe you haven't included all relevant data, but I do not see anywhere in your code where you execute the function you have created.

Instead of what you are currently doing, try this:

echo htmlentities ('<iframe src="http://www.youtube.com/embed/'.getYoutubeVideoID($url).'" frameborder="0" width="'.$wdth.'" height="'.$hth.'"></iframe>');

You can't simply define a function and it will execute and assign variables.. what you have has the function, when it is executed, return a variable in it's place. As an example, you could assign $var the return value of your function:

$var = getYoutubeVideoID($url);

Instead of the very above, you could even try this:

$sVideoID = getYoutubeVideoID($url);

Lastly, instead of using regex as others have noted, you could use parse_url() in combination with parse_str() to get the data from your url:

$arr = parse_url($url);
parse_str($arr['query'], $output);
echo $output['v'];

How come i am getting no value result for $sVideoID

You never assign it (at least not in the code you provided). The code for $sVideoID is inside a user defined function - getYoutubeVideoID(). Which you are never calling. Daedalus provided a sample resolution in his answer.

As an aside… Don't parse the URL with a Regular Expression. There are other, easier ways

For example: