Due to Google AMP (Accelerated Mobile Pages) , I have been looking for a way to effectively do Syntax Highlighting without Javascript in pure PHP.

I was about to write my own, when I found an older article from phoboslab. Thanks Dominic for saving me some time ;) Its not perfect, but close enough.

A simple Syntax Highlighting Class that does just that. The class was not working with PHP 5.4.x+, as it uses preg_replace() with the /e modifier.

It will not cover all, but its better than nothing :) I will also add a section to my my AMP tweaks article to showcase the integration of Geshi.

Here an updated version using the preg_replace_callback() function.

THE SYNTAX HIGHLIGHT CLASS

class SyntaxHighlight {
   
    static $tokens = array();// This array will be filled from the regexp-callback

    public static function process($s) {
        $s = htmlspecialchars($s);

        // Workaround for escaped backslashes
        $s = str_replace('\\\\','\\\\<e>', $s); 

        $regexp = array(

            // Punctuations
            '/([\-\!\%\^\*\(\)\+\|\~\=`\{\}\[\]\:\"\'<>\?\,\.\/]+)/'
            => '<span class="P">$1</span>',

            // Numbers (also look for Hex)
            '/(?<!\w)(
                (0x|\#)[\da-f]+|
                \d+|
                \d+(px|em|cm|mm|rem|s|\%)
            )(?!\w)/ix'
            => '<span class="N">$1</span>',

            // Make the bold assumption that an
            // all uppercase word has a special meaning
            '/(?<!\w|>|\#)(
                [A-Z_0-9]{2,}
            )(?!\w)/x'
            => '<span class="D">$1</span>',

            // Keywords
            '/(?<!\w|\$|\%|\@|>)(
                and|or|xor|for|do|while|foreach|as|return|die|exit|if|then|else|
                elseif|new|delete|try|throw|catch|finally|class|function|string|
                array|object|resource|var|bool|boolean|int|integer|float|double|
                real|string|array|global|const|static|public|private|protected|
                published|extends|switch|true|false|null|void|this|self|struct|
                char|signed|unsigned|short|long
            )(?!\w|=")/ix'
            => '<span class="K">$1</span>',

            // PHP/Perl-Style Vars: $var, %var, @var
            '/(?<!\w)(
                (\$|\%|\@)(\->|\w)+
            )(?!\w)/ix'
            => '<span class="V">$1</span>'

        );      
	
        $s = preg_replace_callback( '/(
                \/\*.*?\*\/|
                \/\/.*?\n|
                \#.[^a-fA-F0-9]+?\n|
                \<\!\-\-[\s\S]+\-\-\>|
                (?<!\\\)&quot;.*?(?<!\\\)&quot;|
                (?<!\\\)\'(.*?)(?<!\\\)\'
            )/isx' , array('SyntaxHighlight', 'replaceId'),$s);
			
        $s = preg_replace(array_keys($regexp), array_values($regexp), $s);

        // Paste the comments and strings back in again
        $s = str_replace(array_keys(SyntaxHighlight::$tokens), array_values(SyntaxHighlight::$tokens), $s);

        // Delete the "Escaped Backslash Workaround Token" (TM)
        // and replace tabs with four spaces.
        $s = str_replace(array('<e>', "\t"), array('', '    '), $s);

        return '<pre>'.$s.'</pre>' ;
    }

    // Regexp-Callback to replace every comment or string with a uniqid and save
    // the matched text in an array
    // This way, strings and comments will be stripped out and wont be processed
    // by the other expressions searching for keywords etc.
     static function replaceId($match) {
        $id = "##r" . uniqid() . "##";
	
        // String or Comment?
        if(substr($match[1], 0, 2) == '//' || substr($match[1], 0, 2) == '/*' || substr($match[1], 0, 2) == '##' || substr($match[1], 0, 7) == '<!--') {
            SyntaxHighlight::$tokens[$id] = '<span class="C">' . $match[1] . '</span>';
        } else {
           SyntaxHighlight::$tokens[$id] = '<span class="S">' . $match[1] . '</span>';
        }
		
        return $id;
    }
}

class SyntaxHighlight {

static $tokens = array();// This array will be filled from the regexp-callback

public static function process($s) {

$s = htmlspecialchars($s);

// Workaround for escaped backslashes

$s = str_replace('\\\\','\\\\<e>', $s);

$regexp = array(

// Punctuations

'/([\-\!\%\^\*\+\|\~\=`\{\}\[\]\:\"\'<>\?\,\.\/]+)/'

=> '$1',

// Numbers (also look for Hex)

'/(?<!\w)(

(0x|\#)[\da-f]+|

\d+|

\d+(px|em|cm|mm|rem|s|\%)

)(?!\w)/ix'

=> '$1',

// Make the bold assumption that an

// all uppercase word has a special meaning

'/(?<!\w|>|\#)(

[A-Z_0-9]{2,}

)(?!\w)/x'

=> '$1',

// Keywords

'/(?<!\w|\$|\%|\@|>)(

and|or|xor|for|do|while|foreach|as|return|die|exit|if|then|else|

char|signed|unsigned|short|long

)(?!\w|=")/ix'

=> '$1',

// PHP/Perl-Style Vars: $var, %var, @var

'/(?<!\w)(

(\$|\%|\@)(\->|\w)+

)(?!\w)/ix'

=> '$1'

);

$s = preg_replace_callback( '/(

\/\*.*?\*\/|

\/\/.*?\n|

\#.[^a-fA-F0-9]+?\n|

\<\!\-\-[\s\S]+\-\-\>|

(?<!\\\)".*?(?<!\\\)"|

(?<!\\\)\'(.*?)(?<!\\\)\'

)/isx' , array('SyntaxHighlight', 'replaceId'),$s);

$s = preg_replace(array_keys($regexp), array_values($regexp), $s);

// Paste the comments and strings back in again

$s = str_replace(array_keys(SyntaxHighlight::$tokens), array_values(SyntaxHighlight::$tokens), $s);

// Delete the "Escaped Backslash Workaround Token" (TM)

// and replace tabs with four spaces.

$s = str_replace(array('<e>', "\t"), array('', ' '), $s);

return '<pre>'.$s.'</pre>' ;

}

// Regexp-Callback to replace every comment or string with a uniqid and save

// the matched text in an array

// This way, strings and comments will be stripped out and wont be processed

// by the other expressions searching for keywords etc.

static function replaceId($match) {

$id = "##r" . uniqid() . "##";

// String or Comment?

if(substr($match[1], 0, 2) == '//' || substr($match[1], 0, 2) == '/*' || substr($match[1], 0, 2) == '##' || substr($match[1], 0, 7) == '<!--') {

SyntaxHighlight::$tokens[$id] = '' . $match[1] . '';

} else {

SyntaxHighlight::$tokens[$id] = '' . $match[1] . '';

}

return $id;

}

THE CSS

pre { 
	font-family: 'Courier New', 'Bitstream Vera Sans Mono', 'monospace'; 
	font-size: 9pt;
	border-top: 1px solid #333;
	border-bottom: 1px solid #333;
	padding: 0.4em;
	color: #fff;
}
pre span.N{ color:#f2c47f; } /* Numbers */
pre span.S{ color:#42ff00; } /* Strings */
pre span.C{ color:#838383; } /* Comments */
pre span.K{ color:#ff0078; } /* Keywords */
pre span.V{ color:#70d6ff; } /* Vars */
pre span.D{ color:#ff9a5d; } /* Defines */

pre {

font-family: 'Courier New', 'Bitstream Vera Sans Mono', 'monospace';

font-size: 9pt;

border-top: 1px solid #333;

border-bottom: 1px solid #333;

padding: 0.4em;

color: #fff;

}

pre span.N{ color:#f2c47f; } /* Numbers */

pre span.S{ color:#42ff00; } /* Strings */

pre span.C{ color:#838383; } /* Comments */

pre span.K{ color:#ff0078; } /* Keywords */

pre span.V{ color:#70d6ff; } /* Vars */

pre span.D{ color:#ff9a5d; } /* Defines */

USAGE

echo SyntaxHighlight::process( $your_code );

1	echo SyntaxHighlight::process( $your_code );

@GitHub portalzine/UtilityBelt/SyntaxHighlight

Generic Syntax Highlighting with Regular Expressions in pure PHP

THE SYNTAX HIGHLIGHT CLASS

THE CSS

USAGE

Enjoy coding …

Alexander