Let’s say you were given a task to validate an IP address in a custom script. One approach is to use regular expressions and use pattern matching to see if user input is correct or not. In this example, we will use a regular expression below to validate IP addresses.
We assume user input is done via a form. First things first, we need to sanitize the input. Once sanitized, we can then test the input against the regular expression using a PHP function called the ereg().
// the regular expression for valid ip addresses $reg_ex = '/^((?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))*$/'; // sanitize input from form $ip_address = addslashes(htmlspecialchars(strip_tags(trim($_POST['ip_address'])))); // test input against the regular expression if (ereg($reg_ex, $ip_address)) { // ip address is valid } else { // ip address is not valid }
The result is, we now have a facility to check the validity of IP addresses. We can now perform additional steps when the IP address is valid, or display errors if the IP address is invalid.

I can now open files in Bluefish by double clicking a PHP file from within Nautilus. It’s no longer a blank document. Once again, this is workaround. It will disable opening up project files. I don’t use it, which is fine by me.
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