How PHP uses regular text to navigate directories

There may be many children's shoes interested in directory navigation, click on the above directory text can quickly jump to the relevant content, suitable for long articles or articles with special needs. With regular expressions, automatic article content extracts text with H2 tags as a directory index.

$str = ' 

Array (    [0] = = Array        (            [0] = 

Write a function

function Article_index ($content) {$matches = array ();    $ul _li = "; $r = '/