For example, I want date in this format

Use format string "Y-m-d"

format. preg_match('/line1\r\ntheme_name:([\s\S]*?)\r\nline3/', $text, $matches); The matches ... Match text between two lines, suppose we have three lines of text line1 theme_name:theme1 ... line3 We want to extract out the theme name, here the "theme1" string. We use windows line ending ... will looks like Array ( [0] => line1 theme_name:theme1 line3 [1] => theme1 )

Here is a sample html file contains only "p" and "div" tag:

And we want to insert content into the html, we don't want undermine the html structure, we wish to delimit it in terms of html element, not just characters. We also want to know the positions we want to insert the content. We can use PREG_OFFSET_CAPTURE: