wrap -tag around first word of string with preg_replace

Answer 1

Try with this instead

preg_replace('/(?<=\>)\b\w*\b|^\w*\b/', '<b>$0</b>', $string);

$0 means it will become the first thing matched in your regex, $1 will become the second etc.

You could also use back-references; \0 gets the first thing matched back from where you are, \1 gets the second thing matched back etc. More Info

Answer 2

You need to put a number after $ to refer to grouped part of the regex.Here it would be first group , hence 0. Working example here : http://codepad.org/4V7GWdja

<?php

$string = "an example";
$string = preg_replace('/(?<=\>)\b(\w*)\b|^\w*\b/', '<b>$0</b>', $string);
var_dump($string);

?>

Answer 3

$string = 'an example';
echo preg_replace('/^\b(.+?)\b/i', '<b>$1</b>', $string);

// <b>an</b> example