Simple str_replace() making things wrong - WordPress - php

Question

I need some special filtering to certain text all over my website, like below:
function special_text( $content ) {
$search_for = 'specialtext';
$replace_with = '<span class="special-text"><strong>special</strong>text</span>';
return str_replace( $search_for, $replace_with, $content );
}
add_filter('the_content', 'special_text', 99);
It's doing thing in an excellent way, BUT...
in content if there's any link like: <a title="specialtext" href="http://specialtext.com">specialtext</a> then the title and href texts also changed and the link becomes broken.
How can I make exception there?
Is there a way I can put some exceptions in an array and str_replace() simply skip 'em?

Answer 1

You should use regular expression and use function preg_replace() to replace matched string. Here is the full implementation of your special_text() function.
function special_text( $content ) {
$search_for = 'specialtext';
$replace_with = '<span class="special-text"><strong>special</strong>text</span>';
return preg_replace( '/<a.*?>(*SKIP)(*F)|'.$search_for.'/m', $replace_with, $content );
}
In the following regular expression first, using <a.*?> - everything between <a...> is matched and using (*SKIP)(*F)| it is skipped and then from anything else $search_for is matched (in your case it's specialtext).

Answer 2

Jezzabeanz quite got it except you can simplify it still with:
return preg_replace("/^def/", $replace_with, $content);

Answer 3

If you just want to change the text between the the a tags then a regular expression works wonders.
Here is something I used when I was pulling data from emails sent to me:
(?<=">)(.*?\w)(?=<\/a)
returns "specialtext"
It also returns "specialtext test" if there is whitespace.
Regular expressions are definitely the way to go.
$subject = "abcdef";
$pattern = '/^def/';
preg_match($pattern, $subject, $matches, PREG_OFFSET_CAPTURE, 3);
print_r($matches);
?>
Source
And then do a replace on the returned matches.