正则表达式PHP子模式

Question

I can't get a sub pattern to work

preg_match_all("/<title>(\b\w{4,100}\b)<\/title>/", $input_lines, $output_array);

I want to extract all the words from a title attribute which have more than 3 characters.

If I try the following expressions they both work. But as soon i want to put the last one as a sub pattern it doesn't output anything but 2 empty records in the array.

preg_match_all("/<title>(.*)<\/title>/", $input_lines, $output_array);

preg_match_all("/\b\w{4,100}\b/", $input_lines, $output_array);

I'm using the following text an $input_lines

<title>This is a big test</title>

Answer 1

This is a two-step operation. First extract the title, then get the words.

if( preg_match("(<title>(.*?)</title>)i",$input_lines,$match)) {
    $title = $match[1];
    preg_match_all("/\w{4,}/",$title,$matches);
    $words = $matches[0];
}