Count the number of times a WordPress shortcode is used in a post

Question

I have the following WordPress shortcode function:

function wp_shortcode() {
 static $i=1;
 $return = '['.$i.']';
 $i++;
 return $return;
}
add_shortcode('shortcode', 'wp_shortcode');

This works fine. The $i variable gets incremented each time the function is called in the article. So for

[shortcode][shortcode][shortcode][shortcode]

the output is as expected

[1][2][3][4]

but

if the article has more than one page, than the counter resets on the next article page. So for:

[shortcode][shortcode][shortcode][shortcode]
<!--nextpage-->
[shortcode][shortcode][shortcode][shortcode]

the output is

[1][2][3][4]
<!--nextpage-->
[1][2][3][4]

instead of the wanted output of:

[1][2][3][4]
<!--nextpage-->
[5][6][7][8]

Anyway to change this?

Answer 1

So after researching a bit more @diggy's idea with pre processing the_content and adding the $atts to the shorcodes before the shortcodes are rendered, I came up with this:

function my_shortcode_content( $content ) {
 //check to see if the post has your shortcode, skip do nothing if not found
 if( has_shortcode( $content, 'shortcode' ) ):

  //replace any shortcodes to the basic form ([shortcode 1] back to [shortcode])
  //usefull when the post is edited and more shortcodes are added
  $content = preg_replace('/shortcode .]/', 'shortcode]', $content);

  //loop the content and replace the basic shortcodes with the incremented value
  $content = preg_replace_callback('/shortocode]/', 'rep_count', $content);

 endif;

return $content;
}
add_filter( 'content_save_pre' , 'my_shortcode_content' , 10, 1);

function rep_count($matches) {
 static $i = 1;
return 'shortcode ' . $i++ .']';
}