$10 for solving regex issue

I need to replace some keywords in some text which are enclosed with <p></p>. These keywords will be replaced with links.

To outline the rules:
1. Replace only keywords that are within a <p> and </p>
2. Replace only keywords that are NOT with a <a> and </a>

This is what I got (which performs rule 1):

$patterns[$counter] = "/(<p>.*\b)(".$keyword.")(\b.*<\/p>)/isU";//   
$replacements[$counter] = "$1<a title=\"".$anchorText."\" href=\"".$url."\">$2</a>$3";
.
.
.
$pageContent = preg_replace($patterns, $replacements, $pageContent);

PHP:

However I need to modify the regex patter to include rule 2.

Examples of how this should work for keyword 'piston' and 'cylinder':

It should match this in bold

It should NOT match this in bold

It should match this in bold

It should match this in bold

$10 to the person who can provide the correct regex

 

add me to msn i will help you with this for free

 

bump back up

 

I think you are trying to create SEO optimization.
Just create a inner expression for your pattern code,

just creat a nested condition inside $keyword like , (....)

 

I would try something like this as your pattern:

or maybe don't need all the "(" and ")" so could be simpler :

 

The first part of the regex would match keywords within a link as wel messing up the html.

Anyway, I managed to solve it myself by breaking the regex up into several checking for all combinations of no link, link before, link after, link before and after keyword within a paragraph

Question closed.