$find = array(
"'\[cite\](.*?)\[/cite\]'is",
"'\[b\](.*?)\[/b\]'is",
"'\[link\](.*?)\[/link\]'i",
"'\[link=(.*?)\](.*?)\[/link\]'i",
"'\[img\](.*?)\[/img\]'i"
);

$replace = array(
"<cite>\\1</cite>",
"<b>\\1</b>",
"<a href=\"\\1\" target=\"_blank\">\\1</a>",
"<a href=\"\\1\" target=\"_blank\">\\2</a>",
"<img src=\"\\1\">"
); 

$tekst = preg_replace($find, $replace, $tekst);
$meg = preg_replace($find, $replace, $meg); 
$siden = preg_replace($find, $replace, $siden); 
$interesser = preg_replace($find, $replace, $interesser);