CHAPTER 11
Validation
As you saw in previous chapters,many web applications involve user input.Sadly,however,users make mistakes:they skip required fields,they enter phone numbers with the wrong number of digits,and they send to your application all manner of incorrectly formatted data.Your database routines can choke on corrupted data,and orders can be lost,for example,if a credit card number is entered incorrectly or an address is omitted,so it is imperative to validate userinput.
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