Automatically add Alt Tag to WordPress Image Uploads

functions.php

<?php

/*
Automatically add Alt Tag to WordPress Image Uploads
/* ------------------------------------ */

add_action( 'add_attachment', 'ced_add_image_meta_data' );

function ced_add_image_meta_data( $attachment_ID ) {

	 $filename   =   $_REQUEST['name'];
	 $withoutExt =   preg_replace('/\\.[^.\\s]{3,4}$/', '', $filename);
	 $withoutExt =   str_replace(array('\'','_'), ' ', $withoutExt);

	$my_post = array(
		'ID'           => $attachment_ID,
	);
	wp_update_post( $my_post );
	update_post_meta($attachment_ID, '_wp_attachment_image_alt', $withoutExt );
}
?>