PHP - Moved: Finding Percentage In String

I have a DB of data: article-id, section-id, subsection-id, article-text. When a row is fetched I am displaying article, section, subsection as <h3>, <h4>, <h5> and then text in a <p>. Before outputting the text I want to scan it for other articles, sections, or subsections it may reference then turn that reference into a hyperlink. I read the PHP documentation but I can't find anything that translates to the basic commands of instring, indexof, and left/mid/right. 

Example:

1. Article Name

100. Article 1, section 1

100.a article 1, section 1, subsection a

Text blah blah blah 105.f blah blah blah

I want to find that 105.f and turn it into a link. All my articles, sections, and subsections are in the DB so I know I can use an array of the number values as my items to look for, but I can't figure out how to look.

Hi, and thanks for any help with this. 

I have this but of php i have been trying relentlessly to get working.. for over a month.
 

<?php
$abs="one two three four words";
$mT = "testing for matching words";

$words=explode(' ', $abs);
//$sf=($words);


if (preg_match($words, $mT))
{
        echo "the url $mT contains a Word";
}
else
{
        echo "the url $mT does Not contain a Word";

echo "$words[4]";

}
?>

You see, I get a responce only using the last line "$words[4]", (obviously, because I am pointing it the Matching word, (ie: with [4])
What i need to have is that the script will automatically "find" that Matching Word for me with ANYwhere of the string of $abs (not just the beginning or the ending)". 

not making it confusing, but the obvious word in this I am looking to find is the word, "words".
😕

Thanks so much for any help.