How Can I Replace Whole Words in a String Using PHP and Regular Expressions?

Replacing Whole Word Matches in a String

When attempting to replace a specific word within a string using PHP's str_replace() function, it sometimes replaces parts of words instead of entire words. This undesired behavior can occur when the word or phrase to be replaced appears within longer words.

To resolve this issue, regular expressions can be employed. Regular expressions provide more granular control over the search and replace process. By incorporating the b metacharacter, which matches word boundaries, you can ensure that only whole word matches are replaced.

Solution:

$text = preg_replace('/\bHello\b/', 'NEW', $text);

In this code, bHellob matches complete occurrences of the word "Hello," as indicated by the word boundaries. This ensures that the replacement only occurs when "Hello" is an independent word.

Unicode Considerations:

If the string contains UTF-8 characters, the "u" (Unicode) modifier must be added to the regular expression, as shown below:

$text = preg_replace('/\bHello\b/u', 'NEW', $text);

This modifier ensures that non-Latin characters are not misinterpreted as word boundaries, resulting in accurate replacements.

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