How to Extract Specific CSS Classes with PHP?

Parsing CSS with PHP for Selective Class Extraction

In this article, we aim to tackle the challenge of parsing a CSS file and extracting specific class names that contain a predefined string. We seek a solution in PHP that accomplishes this task effectively.

Problem Statement:

We want to parse a CSS file and identify all class names containing "postclass" in their names. The desired output is an array of these class names, as seen below:

arrayentry1:
#content.postclass-subcontent
arrayentry2:
#content2.postclass-subcontent2

Regular Expressions Approach:

One common approach to parsing CSS is utilizing regular expressions. However, for this specific requirement, regular expressions might not be the most suitable option. The provided sample CSS contains multiple selectors with complex structure, making it challenging to extract the desired class names accurately using regular expressions alone.

PHP-Based Solution:

Instead of relying solely on regular expressions, we present a PHP-based solution that simplifies the parsing process:

function parse($file){
    $css = file_get_contents($file);
    preg_match_all( '/(?ims)([a-z0-9\s\.\:#_\-@,]+)\{([^\}]*)\}/', $css, $arr);
    $result = array();
    foreach ($arr[0] as $i => $x){
        $selector = trim($arr[1][$i]);
        $rules = explode(';', trim($arr[2][$i]));
        $rules_arr = array();
        foreach ($rules as $strRule){
            if (!empty($strRule)){
                $rule = explode(":", $strRule);
                $rules_arr[trim($rule[0])] = trim($rule[1]);
            }
        }

        $selectors = explode(',', trim($selector));
        foreach ($selectors as $strSel){
            $result[$strSel] = $rules_arr;
        }
    }
    return $result;
}

Usage:

To utilize this solution, retrieve the CSS file contents into a variable. Then, call the parse() function with the file contents as an argument. This function returns an array containing the desired class names as keys and their rules as values. For instance:

$css = parse('css/'.$user['blog'].'.php');
$css['#selector']['color'];

This approach allows for a more dynamic and targeted parsing of CSS files, making it flexible for various parsing requirements.

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