html -> bbcode function

[sabret00the]

PHP Code:

        $message = "Reporting Post: [url=viewthread.php?$session[sessionurl]g=$g&#post$p]Post ID #$p[/url]\n\nReason: htmlspecialchars($reason)"; 


this line is spitting out an error, so i'm thinking

PHP Code:

        $message = "Reporting Post: <a href=\"viewthread.php?$session[sessionurl]g=$g&amp;#post$p\">Post ID #$p</a>\n\nReason: htmlspecialchars($reason)"; 


but in order to do that i need to convert the html to bbcode, and i'm sure i've seen a function for it but can't find it, does anyone know what it is?