如何使用Facebook，LinkedIn和Twitter共享按钮共享当前页面？

Question

I'm sorry if this question has already been asked but this case is different. I'm trying to make a Facebook button that is sharing the current URL but I have no idea how to do this.My question is : What should I put instead of 'homepage' so that these buttons share the page the user is currently on instead of a specific URL ? Here's what the current code looks like (I replaced the website's URL by homepage) :

  <a href="http://www.facebook.com/sharer.php?u='homepage' target="_blank" style="text-decoration:none">
    <img src="http://image.noelshack.com/fichiers/2015/25/1434621881-iconmonstr-facebook-4-icon-32.png" alt="Facebook">
</a>

<!-- LinkedIn -->
<a href="http://www.linkedin.com/shareArticle?mini=true&amp;url=homepage" target="_blank" style="text-decoration:none">
    <img src="http://image.noelshack.com/fichiers/2015/25/1434621881-iconmonstr-linkedin-4-icon-32.png" alt="LinkedIn">
</a>

<!-- Twitter -->
<a href="https://twitter.com/share?url=homepage" target="_blank" style="text-decoration:none">
    <img src="http://image.noelshack.com/fichiers/2015/25/1434621881-iconmonstr-twitter-4-icon-32.png" alt="Twitter">
</a>

Answer 1

// Get the current URL
<?php
$Url = (@$_SERVER["HTTPS"] == "on") ? "https://" : "http://";
$Url .= $_SERVER["SERVER_NAME"] . $_SERVER["REQUEST_URI"];
?>
<a href="http://www.facebook.com/sharer.php?u=<?php echo $Url; ?>" target="_blank" style="text-decoration:none">
    <img src="http://image.noelshack.com/fichiers/2015/25/1434621881-iconmonstr-facebook-4-icon-32.png" alt="Facebook">
</a>

<!-- LinkedIn -->
<a href="http://www.linkedin.com/shareArticle?mini=true&amp;url=<?php echo $Url; ?>" target="_blank" style="text-decoration:none">
    <img src="http://image.noelshack.com/fichiers/2015/25/1434621881-iconmonstr-linkedin-4-icon-32.png" alt="LinkedIn">
</a>

<!-- Twitter -->
<a href="https://twitter.com/share?url=<?php echo $Url; ?>" target="_blank" style="text-decoration:none">
    <img src="http://image.noelshack.com/fichiers/2015/25/1434621881-iconmonstr-twitter-4-icon-32.png" alt="Twitter">
</a>