Customize WordPress comment form output

functions.php

<?php

/**
 * Rewrite the HTML for the author, email, and url comment fields
 */
function custom_comment_fields( $fields ) {

	// https://codex.wordpress.org/Function_Reference/comment_form

	$commenter = wp_get_current_commenter();

	$req      = get_option( 'require_name_email' );
	$aria_req = ( $req ? " aria-required='true'" : '' );
	$html_req = ( $req ? " required='required'" : '' );
	$html5    = current_theme_supports( 'html5', 'comment-form' );

	$fields['author'] = '<p class="comment-form-author">' . '<label for="author">' . __( 'Name' ) . ( $req ? ' <span class="required">*</span>' : '' ) . '</label> ' . '<input id="author" name="author" type="text" value="' . esc_attr( $commenter['comment_author'] ) . '" size="30" maxlength="245"' . $aria_req .  $html_req . ' /></p>';

	$fields['email']  = '<p class="comment-form-email"><label for="email">' . __( 'Email' ) . ( $req ? ' <span class="required">*</span>' : '' ) . '</label> ' . '<input id="email" name="email" ' . ( $html5 ? 'type="email"' : 'type="text"' ) . ' value="' . esc_attr(  $commenter['comment_author_email'] ) . '" size="30" maxlength="100" aria-describedby="email-notes"' . $aria_req . $html_req  . ' /></p>';

	$fields['url'] = '<p class="comment-form-url"><label for="url">' . __( 'Website' ) . '</label> ' . '<input id="url" name="url" ' . ( $html5 ? 'type="url"' : 'type="text"' ) . ' value="' . esc_attr( $commenter['comment_author_url'] ) . '" size="30" maxlength="200" /></p>';

	return $fields;

}
add_filter( 'comment_form_default_fields', 'custom_comment_fields' );



/**
 * Rewrite the HTML for the comment textarea field
 */
function custom_comment_form_defaults( $defaults ) {

	// https://codex.wordpress.org/Function_Reference/comment_form

	$defaults['comment_field'] = '<p class="comment-form-comment"><label for="comment">' . _x( 'Comment', 'noun' ) . '</label><textarea id="comment" name="comment" cols="45" rows="8" aria-required="true"></textarea></p>';
	return $defaults;
}
add_filter( 'comment_form_defaults', 'custom_comment_form_defaults' );



/**
 * Re-order the comment fields that get displayed
 */
function reorder_comment_form_fields( $comment_fields ) {
	$new_comment_fields = array(
		'author'  => $comment_fields['author'],
		'email'   => $comment_fields['email'],
		'url'     => $comment_fields['url'],
		'comment' => $comment_fields['comment']
	);
	return $new_comment_fields;
}
add_filter ( 'comment_form_fields', 'reorder_comment_form_fields' );

?>