PHP implements syntax highlighting through regular expressions

function syntax_highlight($code){
 // this matches --> "foobar" <--
 $code = preg_replace(
  &#39;/"(.*?)"/U&#39;, 
  &#39;"<span style="color: #007F00">$1</span>"&#39;, $code
 );
 // hightlight functions and other structures like --> function foobar() <--- 
 $code = preg_replace(
  &#39;/(\s)\b(.*?)((\b|\s)\()/U&#39;, 
  &#39;$1<span style="color: #0000ff">$2</span>$3&#39;, 
  $code
 );
 // Match comments (like /* */): 
 $code = preg_replace(
  &#39;/(\/\/)(.+)\s/&#39;, 
  &#39;<span style="color: #660066; background-color: #FFFCB1;"><i>$0</i></span>&#39;, 
  $code
 );
 $code = preg_replace(
  &#39;/(\/\*.*?\*\/)/s&#39;, 
  &#39;<span style="color: #660066; background-color: #FFFCB1;"><i>$0</i></span>&#39;, 
  $code
 );
 // hightlight braces:
 $code = preg_replace(&#39;/(\(|\[|\{|\}|\]|\)|\->)/&#39;, &#39;<strong>$1</strong>&#39;, $code);
 // hightlight variables $foobar
 $code = preg_replace(
  &#39;/(\$[a-zA-Z0-9_]+)/&#39;, &#39;<span style="color: #0000B3">$1</span>&#39;, $code
 );
 /* The \b in the pattern indicates a word boundary, so only the distinct
 ** word "web" is matched, and not a word partial like "webbing" or "cobweb" 
 */
 // special words and functions
 $code = preg_replace(
  &#39;/\b(print|echo|new|function)\b/&#39;, 
  &#39;<span style="color: #7F007F">$1</span>&#39;, $code
 );
 return $code;
}
/*example-start*/
/*
** Create some example PHP code:
*/
$example_php_code = &#39;
// some code comment:
$example = "foobar";
print $_SERVER["REMOTE_ADDR"];
$array = array(1, 2, 3, 4, 5);
function example_function($str) {
 // reverse string
 echo strrev($obj);
}
print example_function("foo");
/*
** A multiple line comment
*/
print "Something: " . $example;&#39;;
// output the formatted code:
print &#39;<pre class="brush:php;toolbar:false">&#39;;
print syntax_highlight($example_php_code);
print &#39;