Add titles to uploaded images in WordPress

wp_add_img_title.php

/**
 * Sets img title of uploaded attachment.
 * If no title, will use the alt as a defualt title.
 *
 * @param array   $attr Image tag attributes.
 * @param WP_Post $attachment The WP_Post object for the attachment.
 * @link https://developer.wordpress.org/reference/hooks/wp_get_attachment_image_attributes/
 *
 * @return array (maybe) filtered image tag attributes.
 */
function wp_add_img_title( $attr, $attachment = null ) {

	$img_title = trim( wp_strip_all_tags( $attachment->post_title ) );

	$attr['title'] = $img_title ? $img_title : $attr['alt'];

	return $attr;
}
add_filter( 'wp_get_attachment_image_attributes', 'wp_add_img_title', 10, 2 );