PHP Regex problem!

I was creating a Syntax Highlighter in PHP but I was failed! You see when I was creating script comments (//) Syntax Highlighting (gray) , I was facing some problems. So I just created a shortened version of my Syntax Highlighting Function to show you all my problem. See whenever a PHP variable ,i.e., $example, is inserted in between the comment it doesn't get grayed as it should be according to my Syntax Highlighter. You see I'm using preg_replace() to achieve this. But the regex of it which I'm using currently doesn't seem to be right. I tried out almost everything that I know about it, but it doesn't work. See the demo code below.

Problem Demo Code

<?php
  $str = '
  <?php
    //This is a php comment $test and resulted bad!
    $text_cool++;
  ?>
  ';
  $result =开发者_Python百科 str_replace(array('<','>','/'),array('[',']','%%'),$str);
  $result = preg_replace("/%%%%(.*?)(?=(\n))/","<span style=\"color:gray;\">$0</span>",$result);
  $result = preg_replace("/(?<!\"|'|%%%%\w\s\t)[\$](?!\()(.*?)(?=(\W))/","<span style=\"color:green;\">$0</span>",$result);
  $result = str_replace(array('[',']','%%'),array('&lt;','&gt;','/'),$result);
  $resultArray = explode("\n",$result);
  foreach ($resultArray as $i) {
    echo $i.'</br>';
  }
?>

Problem Demo Screen

So you see the result I want is that $test in the comment string of the 'Demo Screen' above should also be colored as gray!(See below.)

Can anyone help me solve this problem?

I'm Aware of highlight_string() function!

THANKS IN ADVANCE!

Reinventing the wheel?

highlight_string()

Also, this is why they have parsers, and regex (despite popular demand) should not be used as a parser.

I agree, that you should use existing, parsers. Every ide has a php parser, and many people have written more of them.

That said, I do think it is worth the mental exercise. So, you can replace:

$result = preg_replace("/(?<!\"|')[\$](?!\()(.*?)(?=(\W))/","<span style=\"color:green;\">$0</span>",$result);

with

//regular expression.:
//#([^(%%%%|\"|')]*)([\$](?!\()(.*?)(?=(\W)))#

//replacement text:
//$1<span style=\"color:green;\">$2</span>

$result = preg_replace("#([^(%%%%|\"|')]*)([\$](?!\()(.*?)(?=(\W)))#","$1<span style=\"color:green;\">$2</span>",$result);

Personally, I think your best bet is to use CSS selectors. Replace style=\"color:gray;\" with class="comment-text" and style=\"color:green;\" with class="variable-text" and this CSS should work for you:

.variable-text {
    color: #00E;
}
.comment-text .comment-text.variable-text {
    color: #DDD;
}

Insert don't use regex to parse irregular languages here

anyway, it looks like you've run into a prime example of why regular expressions are not suited for this kind of problem. You'd be better off looking into PHP's highlight_string functionality

Well, you don't seem to care that php already has a function like this.

But because of the structure of php code one cannot simply use a regex for this or walk into mordor (the latter being the easier).

You have to use a parser or you will fly over the cuckoo's nest soon.