Validating html forms before processing to a php script
The media has helped make cross-site scripting (XSS) a familiar term, and the attention is deserved.
It is one of the most common security vulnerabilities in web applications, and many popular open source PHP applications suffer from constant XSS vulnerabilities.
You'll see that the all validation scripts presented on this and subsequent pages adhere to the same basic format.
When form input is important, it should always be verified using a secure server-side script.
I've coded a working form, all checks are great but for some reason the hardest part is trying to stop form submission before validation.
So i have places to insert the stop validation code, but just cant find any that works.
Radio buttons are implemented as if they were an array of checkboxes.
To find out which value (if any) has been selected, you need to loop through the array until you find which one has been selected: In the case of a single radio button we have nothing to loop through so just return either it's value, if the radio button is checked, or false.
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Normally you would modify this so that you could submit or not submit the form based on the number of items selected. For example, a text input that only needs to have a value if a checkbox is checked: Using simple logical operators and the functions supplied above you can do all sorts of client-side form validation.