Dynamic WordPress FAQPage Rich Snippets - use this in a plugin or functions.php

FAQPage-rich-snippets.php

<?PHP
function add_rich_snippets_content( $content ) {    
	global $post;
	
    $post_ID   		= $post->ID;
    $page_title   	= get_the_title ( $post_ID );
    
    $page_object 	= get_post( $post_ID );
	$page_excerpt 	= wp_strip_all_tags ( $page_object->post_content );
	$page_excerpt   = preg_split ("/\s/", $page_excerpt);
	
	$page_excerpt2 ="";
	for ( $j=0; $j<65; $j++ ){
		$page_excerpt2 .= $page_excerpt[ $j ] . " ";
	}

	$flag 			= in_category("blog-seo");
	if ( $flag==1 ) {
	
	$titolo_domanda = $page_title;
	$risposta = $page_excerpt2;
	
	$code = '	
<script type="application/ld+json">
{
  "@context": "https://schema.org",
  "@type": "FAQPage",
  "mainEntity": [
    {
      "@type": "Question",
      "name": "'.$titolo_domanda.'",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "'.$risposta.'"
      }
    }
  ]
}
</script>
	';
	
	$content .= $code;
	}
	
	return $content;
}
add_filter( 'the_content', 'add_rich_snippets_content',100 );

?>