Alternatives to GUID with PHP

GUID stands for Globally Unique Identifier. It is a string of letters and numbers and useful to allow website visitors to access a site without needing a username and password because although the probability that a GUID will be duplicated is not zero, it is close enough to zero to be negligible.

In fact Wikipedia says that you would have to generate 2.71 Quintillion (an 18 digit number) GUIDs to have a 50% probability of a collision.

However a GUID isn’t pretty, they look like 204FA460-65C6-DAB0-C69E-013ECE71F5D0 which can be scary to non-technical users when used in a URL.

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WordPress WooCommerce SagePay mcrypt

WordPress WooCommerce SagePay Form extension https://woocommerce.com/products/sage-pay-form/ requires the PHP mcrypt extension to operate.

If your site uses this extension and one day stops going through the full checkout process be aware of the following:

mcrypt has been deprecated as of PHP 7.1.0 and will be moved to PECL as of PHP 7.2.0 – this is because it relies upon libmcrypt which is dead and unmaintained since 2007 http://php.net/manual/en/intro.mcrypt.php.

Your host may have disabled the mcrypt extension.

I’ve heard that the WooCommerce SagePay Form extension is currently being updated to use openssl_encrypt so there may be an update soon to rectify this.