highlight text with surrounding words

Question

i want to highlight text in a given string with given keywords and add a random number of surrounding words.

Example sentence:

Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed.

Example keyword:

dolore magna

Desired result: (mark 0-4 words before and after the keyword

Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et **dolore magna** aliquyam erat, sed.

What did i try?

( [\w,\.-\?]+){0,5} ".$myKeyword." (.+ ){2,5} and ([a-zA-Z,. ]+){1,3} ".$n." ([a-zA-Z,. ]+){1,3}

Any ideas how to improve this and make it more robust?

Answer 1

For highlighting use preg_replace function. Here's an idea:   $s = "dolore magna";

$str = preg_replace(
       '/\b(?>[\'\w-]+\W+){0,4}'.preg_quote($s, "/").'(?:\W+[\'\w-]+){0,4}/i',
       '<b>$0</b>', $str);

Test the pattern at regex101 or php test at eval.in.   echo $str;

Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed.

Using i flag for caseless matching - drop if not wanted. First group ?> atomic for performance.

• As word character I used ['\w-] (\w shorthand for word character, ' and -)
• \W matches a character, that is not a word character (negated \w)
• \b matches a word boundary. Used it for better performance.

Answer 2

I think this would accomplish what you are after. Please see the demo for an explanation of everything the regex is doing, or post a comment if you have a question.

Regex:

((?:[\w,.\-?]+\h){0,5})\b' . . '\b((?:.+\h){2,5})

Demo: https://regex101.com/r/vG8qT2/1

PHP:

<?php
$string = 'Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed.';
$term = 'dolore magna';
$min = 0;
$max = 5;
preg_match('~((?:[\w,.\-?]+\h){'.$min.','.$max. '})\b' . preg_quote($term) . '\b((?:.+\h){'.$min.','.$max.'})~', $string, $matches);
print_r($matches);

Demo: https://eval.in/410063

Note the captured values will be in $matches[1] and $matches[2].