Pro PHP and jQuery by Jason Lengstorf.pdf - Computer Science ...

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CHAPTER 9 ■ PERFORMING FORM VALIDATION WITH REGULAR EXPRESSIONS
Figure 9-14. The completed regular expression
■ Tip The examples in this chapter go over the most common features of regular expressions, but they don’t
cover everything that regexes have to offer. Jan Goyvaerts has put together a fantastic resource for learning all of
the ins-and-outs of regexes, as well as some tools for testing them, at
http://www.regular-expressions.info/.
Adding Server-Side Date Validation
Now that you have a basic understanding of regexes, you’re ready to start validating user input. For this
app, you need to ensure that the date format is correct, so that the app doesn’t crash by attempting to
parse a date that it can’t understand.
You’ll begin by adding server-side validation. This is more of a fallback because later you’ll add
validation with jQuery. However, you should never rely solely on JavaScript to validate user input
because the user can easily turn off JavaScript support and therefore completely disable your JavaScript
validation efforts.
Defining the Regex Pattern to Validate Dates
The first step toward implementing date validation is to define a regex pattern to match the desired
format. The format the calendar app uses is YYYY-MM-DD HH:MM:SS.
Setting up Test Data
You need to modify regex.php with a valid date format and a few invalid formats, so you can test your
pattern. Start by matching zero or more numeric characters with your regex pattern. Do this by making
the following changes shown in bold: