voku/remove_first_html_tag.php

## remove_first_html_tag.php
<?php

$input_lines = ' <div>da<a>
  lalll
</a>sda
</div>';

$output = preg_replace('/^<(?<element_start>[a-z]+)(?<element_start_addon> [^>]*)?>(?<value>.*?)<\/(?<element_end>\1)>$/usi', '$3', trim($input_lines));


echo $output;
/*
da<a>
  lalll
</a>sda
*/
	<?php

	$input_lines = ' <div>da<a>
	lalll
	</a>sda
	</div>';

	$output = preg_replace('/^<(?<element_start>[a-z]+)(?<element_start_addon> [^>])?>(?<value>.?)<\/(?<element_end>\1)>$/usi', '$3', trim($input_lines));


	echo $output;
	/*
	da<a>
	lalll
	</a>sda
	*/