Regualr Expression validation with javascript or php ?

we are learning php..i have got a registration page in which the email entered from the user has to be validated..this should ideally be done with server employing php or on the client once more with javascript

It should be done in both.Relying upon client-site validation has the potential health risks that we doesn’t service JavaScript or maybe some “naughty” customers purposely bypass the validation.So server-side validation is utterly necessary.

Still adding your client-side validation, even so, is good in this it can reduce your server place.So this server-side validation is types of 2nd a higher level validation to filter out inputs who were tampered by using or inputs from clients that do not support JavaScript.