匹配用空格分隔的字母数字字符

Question

Okay, I'm stuck. PHP, Regex. I have a string:

Это кириллические 23 78these are56 45latin76 letters here98 85 буквы.

And I want to use preg_replace() to enclose a substring containing latin letters, numbers and spaces with <b> tags. A substring is not merely a word but a set of words as long as the next word contains Latin characters:

Это кириллические 23 78these are56 45latin76 letters here98 85 буквы.

My best shot was:

$text = 'Это кириллические 23 78these are56 45latin76 letters here98 85 буквы.';
$regex = "/\d*\p{Latin}+(\d|\s|\p{Latin})*/iu";
preg_replace($regex, '<b>$0</b>', $text);

But it grabs not only "here98" but also the following "85":

Это кириллические 23 78these are56 45latin76 letters here98 85 буквы.

I understand why it is so but fail to figure out the correct Regex.

Answer 1

You need not just match Latin+digits words, but look one word ahead and one word behind. AFAIK, variable-length look-behinds are not possible, so you should use non-capturing group (?:...)and positive look-ahead (?=...):

$regex = "/(?:[\p{Latin}\d]+ )([\p{Latin}\d ]+)(?= [\p{Latin}\d]+)/iu";
preg_replace($regex, '<b>$1</b>', $text);

PS: Aaaah! Russian mafia! ;-)