Extract shortcode parameters in content – WordPress

Think about a post content like below:

[shortcode a="a_param"]
... Some content and shortcodes here
[shortcode b="b_param"]
.. Again some content here
[shortcode c="c_param"]

I have a shortcode that takes 3 or more parameters. I want to find out how many times the shortcode is used at the content and its parameters in an array like,

array (
[0] => array(a => a_param, b=> null, c=>null),
[1] => array(a => null, b=> b_param, c=>null),
[2] => array(a => null, b=> null, c=>c_param),
)

I need to do this in the_content filter, wp_head filter or something similar.

How can I do this ?

Thank you,

Answer

In wordpress get_shortcode_regex() function returns regular expression used to search for shortcodes inside posts.

$pattern = get_shortcode_regex();

Then preg_match the pattern with the post content

if (   preg_match_all( '/'. $pattern .'/s', $post->post_content, $matches ) )

If it return true, then extracted shortcode details are saved in $matches variable.

Try

global $post;
$result = array();
//get shortcode regex pattern wordpress function
$pattern = get_shortcode_regex();


if (   preg_match_all( '/'. $pattern .'/s', $post->post_content, $matches ) )
{
    $keys = array();
    $result = array();
    foreach( $matches[0] as $key => $value) {
        // $matches[3] return the shortcode attribute as string
        // replace space with '&' for parse_str() function
        $get = str_replace(" ", "&" , $matches[3][$key] );
        parse_str($get, $output);

        //get all shortcode attribute keys
        $keys = array_unique( array_merge(  $keys, array_keys($output)) );
        $result[] = $output;

    }
    //var_dump($result);
    if( $keys && $result ) {
        // Loop the result array and add the missing shortcode attribute key
        foreach ($result as $key => $value) {
            // Loop the shortcode attribute key
            foreach ($keys as $attr_key) {
                $result[$key][$attr_key] = isset( $result[$key][$attr_key] ) ? $result[$key][$attr_key] : NULL;
            }
            //sort the array key
            ksort( $result[$key]);              
        }
    }

    //display the result
    print_r($result);


}