HTML whitespace trim RegEx (regular expression) for PHP. Useful for trimming HTML content before TCPDF processing.

html_trim_whitespace.php

<?php

// Trims whitespaces after any tags. Assumes that a tag ends with '/>', '\w>', '">'.
$html = preg_replace('#(["|\/|\w]>)(\s+)#', '$1', $html);

// Trims whitespaces before any tags. Assumes that tags start with '<\w+'
$html = preg_replace('#(\s+)(<\/?\w+)#', '$2', $html);

// Trims spaces between tags (both opening and closing).
// Assumes that a tag ends with '/>', '\w>', '">' and starts with '<\w+'
$html = preg_replace('#(["|\/|\w]>)(\s+)(<\/?\w+)#', '$1$3', $html);