question concerning preg_replace

hi all

i’ve gotten into regular expressions recently, read lots of tutorials and got my hands dirty trying to figure out how to properly replace text using a plugin. i would like to know if there’s a more elegant way to do the following.

i want to insert an image tag right before a specified string, but only if that string appears inside a particular tag. for example:

<p class="foo">this is an example</p>

i want to add an image tag right before the word “example”, but only when the word “example” is inside a class=”foo” paragraph. after many trials and errors, i’ve come up with the following function which is called through an add_filter (for the sake of simplicity, i call the image tag in this example <img>):

$string equals the_content in this example

function testing($string) {
$pattern = '/<p class=\"foo\">(.*?)(example)(.*?)<\/p>/i';
$replace = '<p class="foo">\1<img>\2\3</p>';
$string = preg_replace($pattern,$replace,$string);
return $string;
}

since this is newbie stuff, i’d like to know if i’m (wrongly) reinventing the wheel or if i’ve come to the right place.

thanks.