Restrict characters in comment section

Question

I am using Travelify theme and I am having some trouble restricting the characters in the comment section (textarea) or where the name or mail goes into the input tags.

I read some articles about changing the core files from wp-includes like post.php / post-formats.php / formatting.php , for changing the preg_match function and only allow a-zA-Z0-9 and some other like .,? characters or others to be used.And i would also like to add a text that appears that dosen't allow special characters.

I know that is not the best practice to change the core files, but some times it can help you.

Answer 1

Never edit the WordPress core files.

Instead you should hook into the pre_comment_content, which is where the comment text from the textarea is being sanitized, before it's inserted into the database.

In the example below preg_replace is used to sanitize the comment text submitted. You should modify the function to fit your needs.

function keha_filter_comment( $comment_content ) {
    $comment_sanitized = preg_replace( "/[^0-9a-zA-Z ]/", "", $comment_content );
    return $comment_sanitzed;
}
add_action( 'pre_comment_content', 'keha_filter_comment' );

There are also some other filter hooks available for the other comment fields available, you can find them within the WordPress code, look for the apply_filters, also listed below:

• pre_comment_author_name
• pre_comment_user_ip
• pre_comment_author_url
• pre_comment_author_email
• pre_comment_content