Here is the top answer of How to display HTML tags as plain text
<?php
$patterns = array();
$patterns[0] = '/</';
$patterns[1] = '/>/';
$replacements = array();
$replacements[2] = '<';
$replacements[1] = '>';
preg_replace($patterns, $replacements, $string);
?>
Replace <
with <
and >
with >