To fill HTML Meta tags on article pages

If you want to optimize the indexing of your site by search engines, you can, for example, include the description of the article, the associated keywords and the name of the authors in the meta tags.

It should be noticed that for the keywords and the authors, we use a nested loop to seek this information for the related id_article. Also, we specify a separating comma so that the contents of the meta tag are comprehensible (including by a search engine).