Automatically Fill Image Alt Text and Metadata in WordPress on Upload

<?php

add_action( 'add_attachment', 'my_set_image_meta_upon_image_upload' );
function my_set_image_meta_upon_image_upload( $post_ID ) {

	// Check if uploaded file is an image, else do nothing

	if ( wp_attachment_is_image( $post_ID ) ) {

		$my_image_title = get_post( $post_ID )->post_title;

		// Sanitize the title:  remove hyphens, underscores & extra spaces:
		$my_image_title = preg_replace( '%s*[-_s]+s*%', ' ',  $my_image_title );

		// Sanitize the title:  capitalize first letter of every word (other letters lower case):
		$my_image_title = ucwords( strtolower( $my_image_title ) );

		// Create an array with the image meta (Title, Caption, Description) to be updated
		// Note:  comment out the Excerpt/Caption or Content/Description lines if not needed
		$my_image_meta = array(
			'ID'		=> $post_ID,			// Specify the image (ID) to be updated
			'post_title'	=> $my_image_title,		// Set image Title to sanitized title
			'post_excerpt'	=> $my_image_title,		// Set image Caption (Excerpt) to sanitized title
			'post_content'	=> $my_image_title,		// Set image Description (Content) to sanitized title
		);

		// Set the image Alt-Text
		update_post_meta( $post_ID, '_wp_attachment_image_alt', $my_image_title );

		// Set the image meta (e.g. Title, Excerpt, Content)
		wp_update_post( $my_image_meta );

	} 
}