Variable events

I have a curious development question, Has PHP ever though of implementing something loosely termed as "event variables" ? I.e. it is basically a variable that you can specify a specific function to execute with the variable as the argument for whenever the variable is created, destroyed, modified or read from. I can think of some fairly useful implications of this and I was wondering if the idea has ever been proposed here. If not, where would PHP need to be modified in order to support this feature. I'm curious in picking up development work if there are no serious issues with this. Thanks, Trevor Trevor F. Linton Systems Administrator/Web Developer Vérité Multimedia Inc. http://www.verite.com DVD * CD * Web * Print * Film * Sound Phone: 801.553.1101 x 111 Fax: 801.553.1215 trevor@verite.com