PHP preg_replace: Keep Heading and Table Together in HTML

This code uses the PHP function 'preg_replace' to search and replace a pattern in an HTML string. The pattern is a regular expression that matches a heading tag (h1 to h6) followed by any attributes, and then followed by any content other than heading tags, until a closing heading tag is found. Immediately after the closing heading tag, the pattern matches a table tag.

The replacement string adds a new attribute 'keep-with-table' to the heading tag, with the value '1'. This attribute can be used in CSS to ensure that the heading and the following table stay together on the same page when printed or rendered.

Overall, this code modifies the HTML to improve the layout and readability of the content, especially when printed or rendered in a PDF format.