PHP syntax highlighter

Here’s a basic PHP “syntax highlighter” function:

function highlight($string)
{
	$syntax = array(
		array('/([|\"|\'].*[|\"|\'])([^A-Za-z0-9\s])/Us', '<span style="color:#808080;">$1</span>$2'), //Strings
		array('/(\[|\s)([0-9]{1,})(\]|\s)/', '$1<span style="color:#FF8000;">$2</span>$3'), //Numbers
		array('/(\$[a-zA-Z0-9_]+)/', '<span style="color:#000080;">$1</span>'), //Variables
		array('/(\/\*)(.*)(\*\/)/s', '<span style="color:#008000;">$0</span>'), //Multi-line comment
		array('/(\/\/)(.*)(\n)/', '<span style="color:#008000;">$1$2</span>'), //Single line comment
		array('/[\[|\]]/', '<span style="color:#8000FF;">$0</span>'), //Slashes
		array('/[\(|\)]/', '<span style="color:#8000FF;">$0</span>'), //Brackets
		array('/[\[|\]]/', '<span style="color:#8000FF;">$0</span>'), //Square brackets
		array('/[\{|\}]/', '<span style="color:#8000FF;">$0</span>'), //Curly braces
		array('/[\,|\.|\?|\!]/', '<span style="color:#8000FF;">$0</span>'), //Punctuation
		array('/[\£|\^|\&|\-|\+|\%|\@|\~|\`|\¬]/', '<span style="color:#8000FF;">$0</span>'), //Miscellaneous
		array('/\b(?<!\$)(as|break|case|class|const|continue|declare|default|do|echo|else|elseif|endfor|endforeach|endif|endswitch|endwhile|extends|false|for|foreach|function|global|if|include|include_once|interface|namespace|new|null|print|private|protected|public|require|require_once|return|self|switch|throw|true|use|var|while)\b/', '<span style="color:#0000FF; font-weight:bold;">$1</span>') //Key words
	);

	foreach($syntax as $set){
		$string = preg_replace($set[0], $set[1], $string);
	}

	return "<pre>$string</pre>";
}

This is a somewhat rudimentary script, in that it’s not very flexible- I wrote it only with PHP in mind (although it could be easily extended for other languages)- and nor is it very robust. I wrote this as simply as possible, as an exercise in regex patterns more than anything- so it’s not going to be rivaling GeSHi!

In the future when I have an actual need for it, I’ll make modifications and improvements; or more likely, rewrite it from scratch. However, you may find it useful in some way, which is why it’s here.