You can use a shortcode or the_content
filter. I think the_content
filter is better because your don’t introduce any string in your post, so the content can be exported and used in another platforms if needed. For emxample, for show a block of adsense after the first parragraph:
add_filter( 'the_content', 'tbn_ads_inside_content' );
function tbn_ads_inside_content( $content ) {
$output = $content;
//We don't want to modify the_content in de admin area
if( !is_admin() ) {
$ads = "<p>your_ads_code</p>";
$p_array = explode('</p>', $content );
$p_count = 1;
if( !empty( $p_array ) ){
array_splice( $p_array, $p_count, 0, $ads );
$output="";
foreach( $p_array as $key=>$value ){
$output .= $value;
}
}
}
return $output;
}