Double validation PHP and Ajax

[soundsticks]

Currently I'm using Ajax to do the register validation, but I feel if the internet connection is not in good performance, sometime the Ajax is not working and it did make user register with the same username. So how can I do the double checking register validation.

[haku]

Step 1: Add Javascript validation that validates after the user is finished inserting info.

Step 2: Add PHP to check the submitted data when the user submits the form.

[soundsticks]

Step 1: Add Javascript validation that validates after the user is finished inserting info.

Step 2: Add PHP to check the submitted data when the user submits the form.

 

But I'm using Ajax already on my register form and when user try to select/insert the user that he wish it will show whether the username is available or taken by others.  

[haku]

Then you only need to add step 2.

[Psycho]

Step 1: Add Javascript validation that validates after the user is finished inserting info.

Step 2: Add PHP to check the submitted data when the user submits the form.

 

I have to disagree slightly. Server-side validation should be #1 and a requirement. Client-side validation is a "nice to have" but not a necessity, so it should be considered #2.

Edited March 27, 2013 by Psycho

[haku]

You aren't disagreeing with me, in that my list wasn't a list of priorities, it was a list of steps. And there is nothing wrong with reversing those two steps.

[DaveyK]

Client side validation is markup (great for validating charsets and such), server side validation is real deal.

 

However, the signup issue you describe only occurs on ajax calls and not when you try to do it via the traditional method? One method that always work is just making the user name unique in the database table, its not that pretty though (you'd run an UPDATE IGNORE and check how many rows were actually affected to see if the add worked).