Probably (not) the world's most advanced string splitting function.

explode_adv.php

<?php
/*******************************
 * An advanced string splitting function written in PHP.
 * Blog Post: https://starbeamrainbowlabs.com/blog/article.php?article=posts%2F077-PHP-String-Splittting.html
 * Written by Starbeamrainbowlabs.
 * Website: https://starbeamrainbowlabs.com
 * Twitter: @SBRLabs
 */
function explode_adv($openers, $closers, $togglers, $delimiters, $str)
{
	$chars = str_split($str);
	$parts = [];
	$nextpart = "";
	$toggle_states = array_fill_keys($togglers, false); // true = now inside, false = now outside
	$depth = 0;
	foreach($chars as $char)
	{
		if(in_array($char, $openers))
			$depth++;
		elseif(in_array($char, $closers))
			$depth--;
		elseif(in_array($char, $togglers))
		{
			if($toggle_states[$char])
				$depth--; // we are inside a toggle block, leave it and decrease the depth
			else
				// we are outside a toggle block, enter it and increase the depth
				$depth++;
			
			// invert the toggle block state
			$toggle_states[$char] = !$toggle_states[$char];
		}
		else
			$nextpart .= $char;
		
		if($depth < 0) $depth = 0;
		
		if(in_array($char, $delimiters) &&
		   $depth == 0 &&
		   !in_array($char, $closers))
		{
			$parts[] = substr($nextpart, 0, -1);
			$nextpart = "";
		}
	}
	if(strlen($nextpart) > 0)
		$parts[] = $nextpart;
	
	return $parts;
}

?>