php code that uses regex to replace a search phrase or search terms with match

Question

I need to highlight my site content based on a phrase like: "fire and water". I need to put  tags around the phrase wherever it exists completely. And if the words appear individually (not in complete form) they should get a  tag. For example, if the content is:

The world is made of three elements fire and water and air. Fire is hot and water is wet.

The result should be:

The world is made of three elements ``fire and water`` ``and`` air. ``Fire`` is hot ``and`` ``water`` is wet.

I tried using:

$output = preg_replace("/("fire and water)/i", '`<b>`$1`</b>`', $content);   
$output = preg_replace("/(fire|and|water)/i", '`<b>`$1`</b>`', $ouput);

However this produces extra (and unwanted)  tags when the full phrase appears in the content causing a result like this:

``fire`` ``and`` ``water``

I know this won't display any differently on the screen than

``fire and water``

However, big problems are caused when the search phrase contains a ' / '. There must be a way in regex to highlight the full phrase and individual words without doing both at once.

As an aside, the world is made of four (classical) elements: earth, water, air and fire. But since [Earth Wind & Fire](https://www.youtube.com/watch?v=Gs069dndIYk), who knows what to think. — Casimir et Hippolyte, Jul 11 '18 at 20:49

score 3 · Accepted Answer · answered Jul 11 '18 at 18:27

The solution is probably much simpler than you thought:

$input  = 'The world is made of three elements fire and water and air. Fire is hot and water is wet.';

$output = preg_replace("/(fire and water|fire|and|water)/i", '<b>$1</b>',$input);

echo $output;

And the output is:

The world is made of three elements fire and water and air. Fire is hot and water is wet.

The source looks like this:

The world is made of three elements <b>fire and water</b> <b>and</b> air. <b>Fire</b> is hot <b>and</b> <b>water</b> is wet.

The elements are processed in the order they are in.

See also: Escaping a forward slash in a regular expression

php code that uses regex to replace a search phrase or search terms with match

1 Answers1