Ajax: A Beginner s Guide in Java

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Ajax: A Beginner s Guide

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Figure 11-8 Displaying form array data: welcome page

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Okay, let s take a look at what we ve done in a browser You can see the welcome page in Figure 11-8, where the user has entered their name and is just about to click Submit The results page, which reports the user s name, appears in Figure 11-9 Very cool Placing all the code for a PHP application in a single page is a new and powerful skill Next, you ll see another way to test if the welcome page has already been displayed by setting a hidden control in the web page

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Figure 11-9 Displaying form array data: results page

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Validating User Input with Ajax and PHP

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Validating Input from the User

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As the last topic in this chapter, we ll take a look at how to validate data that the user entered into a web page Did they enter their name Is what they typed for their age a number Those are the kinds of questions we ll take up now Here s an overview of the PHP code that you first saw at the beginning of this chapter, indicating how we check for errors and display them as needed:

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check_data(); if(count($errors) != 0){ display_errors(); display_welcome(); } else { process_data(); }

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Let s put this example, checkdataphp, together In this example, the user will be asked to enter their name If they don t enter it but click the Submit button, that ll be considered an error and handled on the server in PHP That means that if the welcome page has already been displayed, we don t need to check whether the text field contains any data, because the welcome page would not be displayed if the text field didn t contain data Instead, we ll use an <"input type=hidden"> control named welcome_already_displayed to keep track of whether or not the welcome page has been displayed This technique may be even better than checking whether a text field has any data, because in some cases you may want to allow the user to leave a text field blank Here s how we check if the welcome page has already been shown, in checkdataphp:

<html> <head> <title> Validating User Data </title> </head> <body> <center> <h1>Validating User Data</h1> < php if(isset($_REQUEST["welcome_already_displayed"])){ > </center> </body> </html>

Ajax: A Beginner s Guide

If there is data waiting for us, we can check that data in a new function, check_data, which will fill an array named $errors with any errors that were found:

<html> <head> <title> Validating User Data </title> </head> <body> <center> <h1>Validating User Data</h1> < php $errors = array(); if(isset($_REQUEST["welcome_already_displayed"])){ check_data(); > </center> </body> </html>

In the check_data function, we start by indicating that the $errors array is a global array, not restricted to the check_data function:

<html> <head> <title> Validating User Data </title> </head> <body> <center> <h1>Validating User Data</h1> < php $errors = array();

11:

Validating User Input with Ajax and PHP

if(isset($_REQUEST["welcome_already_displayed"])){ check_data(); function check_data() { global $errors; } > </center> </body> </html>

Now we re free to check if the user entered any text in the text field and if they did not, we store an error message ( Please enter your name ) in the $errors array:

Ajax: A Beginner s Guide

$errors[] = "<font color='red'>Please enter your name</font>"; } } > </center> </body> </html>

Back in the main part of the code, just after the call to check_data, we see if any errors were stored in the $errors array If so, we display the error(s) with a function named display_ errors, and then display the rest of the welcome page so that the user can try again with a function named display_welcome:

In the display_errors function, we send the current error message(s) back to the browser:

Ajax: A Beginner s Guide in Java Printer Data Matrix 2d barcode in Java Ajax: A Beginner s Guide

Ajax: A Beginner s Guide in Java

Printer Data Matrix 2d barcode in Java Ajax: A Beginner s Guide