PHP 7 Form Processing Guide: How to Get URL Parameters Using the $_GET Array

PHP 7 Form Processing Guide: How to use the $_GET array to obtain URL parameters

Introduction:
In PHP development, it is often necessary to obtain parameters from the URL to perform corresponding operations. In PHP, you can use the $_GET array to obtain URL parameters. This article will introduce how to use the $_GET array correctly and related precautions.

1. What is the $_GET array
$_GET is a predefined global variable in PHP, used to obtain parameters passed through the URL. It is an associative array where the keys are parameter names and the values ​​are parameter values.

2. Use the $_GET array to obtain URL parameters
Before using the $_GET array, you first need to understand how URL parameters are passed. Generally speaking, URL parameters will use the "?" symbol as the starting mark of the parameter, the parameter name and the parameter value are separated by the "=" symbol, and multiple parameters are separated by the "&" symbol. For example, the following URL contains two parameters: name and age.
http://example.com/user.php?name=Tom&age=25

In PHP code, you can use $_GET['parameter name'] to obtain the value of the corresponding parameter. For example, use $_GET['name'] to get "Tom", and use $_GET['age'] to get "25".

The following is a sample code that uses $_GET to obtain URL parameters:

<?php
// 获取name参数的值
$name = $_GET['name'];
echo "Name: " . $name;

// 获取age参数的值
$age = $_GET['age'];
echo "Age: " . $age;
?>

3. Precautions for processing URL parameters

1. Check the existence of parameters
   Before using $_GET to obtain URL parameters, it is best to check the existence of the parameters first. You can use the isset() function to determine whether a parameter exists. For example, the following code will first determine whether the name parameter exists, and then obtain its value:

<?php
if (isset($_GET['name'])) {
    $name = $_GET['name'];
    echo "Name: " . $name;
} else {
    echo "Name parameter is missing";
}
?>

2. Conversion and verification of parameter values
   The obtained parameter value is of string type If you need to convert or verify the parameter value, you can use the corresponding function or method. For example, you can use the intval() function to convert the value of the age parameter to an integer: Security vulnerabilities. You can use functions such as htmlspecialchars() and strip_tags() to filter parameter values ​​to prevent XSS attacks.

4. Summary
3. Using the $_GET array can easily obtain URL parameters, and through some processing, the parameter values ​​can be converted and verified. However, when using the $_GET array, you need to pay attention to the existence check of parameters, conversion and verification of parameter values, and prevention of security vulnerabilities.
   
Note: This article uses PHP 7 as an example, but the $_GET array is also applicable to other versions of PHP.

The above is a guide on how to use the $_GET array to obtain URL parameters. I hope it will be helpful to you in PHP form processing. Happy programming!

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