count_p

function count_p( $insertion, $paragraph_id, $content ) {
        $end_p = '</p>';
        $paragraphs = explode( $end_p, $content );
        foreach ($paragraphs as $index => $paragraph) {
                if ( trim( $paragraph ) ) {
                        $paragraphs[$index] .= $end_p;
                }
                if ( $paragraph_id == $index + 1 ) {
                        $paragraphs[$index] .= $insertion;
                }
        }
 
        return implode( '', $paragraphs );
}