PHP function to convert bbcode to markdown using preg_replace()

bbcode_to_markdown.php

<?php

	function bbcode_to_markdown($input) {

		$result = $input;

		foreach ([

			'#(\r\n?|\n)#s' => '\n', // Neutralize line breaks

			'#\s*\[hr\]\s*#s' => "\n_____\n",

			'#\[b\](.*?)(\[/b\]\s*|$)#s' => "**$1**",

			'#\[u\](.*?)(\[/u\]\s*|$)#s' => "<u>$1</u>",

			'#\[i\](.*?)(\[/i\]\s*|$)#s' => "__$1__",

			'#\s*\[li\](.*?)\[/li\]\s*#s' => "\n    * $1\r\n",

			'#\s*\[ol\](.*?)(\[/ol\]\s*|$)#s' => "\n\n$1\n\n",

			'#\s*\[ul\](.*?)(\[/ul\]\s*|$)#s' => "\n\n$1\n\n",

			'#\s*\[list\](.*?)(\[/list\]\s*|$)#s' => "\n\n$1\n\n",

			'#\[code[^\]*]\](.*?)(\[/code\]|$)#s' => "```$1```",

			'#\[font[^\]*]\](.*?)(\[/font\]|$)#s' => "$1",

			'#\[url](.*?)(\[/url\]|$)#s' => "[$1]($1)",
			'#\[url=([^\]]*)]\](.*?)(\[/url\]|$)#s' => "[$2]($1)",

			'#\[img](.*?)(\[/img\]|$)#s' => "![]($1)",
			'#\[img=([^\]]*)]\](.*?)(\[/img\]|$)#s' => "![$2]($1)",

			'#[\t ]+([\r\n]*)$#m' => '$1', // Trim trailing space

			'#\n\n+#s' => '\n\n', // Remove exceeding line breaks

		] as $pattern => $replace) {
			$result = preg_replace($pattern, $replace, $result);
		}

		return $result;
	}