Validate text input as valid URL for WordPress

wp-get-field-as-link.php

<?php
/**
 * Validate text input as valid URL for WordPress.
 *
 * @param string $text Text from field.
 */
function xx_get_field_as_link( $text ) {
	if ( ! empty( $text ) ) {
		// If first character of link is a /, assume a relative URL
		if ( substr( $text, 0, 1 ) === '/' ) {
			$text = get_home_url() . $text;
		}
		// If field value is an integer, assume it's the page/post ID and get URL
		if ( ctype_digit( $text ) ) {
			$text = get_permalink( $text );
		}
		// Validate button link as a URL
		$url = filter_var( $text, FILTER_VALIDATE_URL ) ? $text : NULL;
		
		return $url;
	}
	return;
}