函数在给定字符串utf-8上设置特定单词的样式？

How to style specific words from a given string ? i hyave a function to style specific words from a given string but this is not working in utf-8 string

 header('Content-type: text/html; charset=utf-8');
function bold($string, $word)
{
    return preg_replace('/\b'.$word.'\b/', '<strong>'.$word.'</strong>', $string);
}

echo bold('چمستان تا', 'تا');

How can i do this ? I need to bold some keyword / phrases in the search resut based on typed user query

Any help would be appreciated

Make sure that:

• Your pages are saved with UTF8 encoding
• Add /u modifier
• Better preg_quote the search word just in case

Use

preg_replace('/\b'.preg_quote($word,'/').'\b/u', '<strong>'.$word.'</strong>', $string);

As an alternative to \b, you may use non-ambiguous word boundaries (no word char before or after the search word are allowed):

preg_replace('/(?<!\w)'.preg_quote($word,'/').'(?!\w)/u', '<strong>'.$word.'</strong>', $string);

or - to enforce the match inside whitespaces:

preg_replace('/(?<!\S)'.preg_quote($word,'/').'(?!\S)/u', '<strong>'.$word.'</strong>', $string);