What potential problem arises when trying to highlight a specific word like "xml" within a larger word like "simplexml" in PHP code?

When trying to highlight a specific word like "xml" within a larger word like "simplexml" in PHP code, the issue arises because using simple string manipulation functions like `str_replace` can inadvertently affect other parts of the word that contain the target word. To solve this problem, you can use regular expressions with word boundaries to ensure that only the specific word "xml" is highlighted without affecting other parts of the string.

$text = "simplexml is a PHP extension for XML processing";
$highlighted_text = preg_replace('/\b(xml)\b/i', '<span style="background-color: yellow;">$1</span>', $text);
echo $highlighted_text;