WordPress Custom php line code

Question

I would like to add a small line of php to a post that already exists in WordPress im aded the code but after im publish it the code automatically convert to comment :

this that im add :

and this what i get :

Answer 1

You can use the shortcodes, add some lines to the file functions then use the shortcode into your post

add_shortcode( 'php_code', function(){
echo "hello world";
} );

then use the [php_code] into your post