Opening a link in new tab or window when the user posts text using a textfield

I have a text area where the users of the system can post anything, even HTML tags. My problem is, when the user posts a link or an anchor tag to a page outside the domain of my website, the user leaves my domain and goes to another site. I don't want this to happen.

I want the link to be opened in a new tab or in a new window, so that the user still remains in my domain. How do I do this?

Here is how the scrap is being displayed:

            if($row2['html']==0)
        echo '<div id="scrap_text"&g开发者_如何学编程t;<pre>'.htmlentities($row2['scrap']).'</pre></div>';
        else
        echo '<div id="scrap_text"><pre>'.$row2['scrap'].'</pre></div>';
        echo '</div>';

And the jQuery is:

$(document).ready(function(){
                                    $("#scrap_text").find("a").attr("target", "_blank");  });

I am not getting the required functionality. The scraps displayed above using PHP, are loaded using placed AJAX. Is it because the div is loaded after the document.ready is being loaded?

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Using JQuery, you can find <a> tags inside of a user post, and then inject the target="_blank" property into them.

Something like this:

$("#post").find("a").attr("target", "_blank");