Magic constants in php

The Magic constant $ _ SERVER of php stores information about the current SERVER. several values are as follows: $ _ SERVER ["QUERY_STRING"], $ _ SERVER ["REQUEST_URI"], $ _ SERVER ["SCRIPT_NAME"] and $ _ SERVER ["PHP_SELF"] are often confusing. The following describes the differences between QUERY_STRING, REQUEST_URI, SCRIPT_NAME, and PHP_SELF variables in the $ _ SERVER function through examples, master the relationships between the four, so that you can correctly obtain the required values in practical applications for your reference.
1, $ _ SERVER ["QUERY_STRING"]
Description: query string
2, $ _ SERVER ["REQUEST_URI"]
Description: the URI required to access this page
3, $ _ SERVER ["SCRIPT_NAME"]
Description: path containing the current script
4, $ _ SERVER ["PHP_SELF"]
Description: file name of the script being executed
Instance:
1, http://www.biuuu.com/(open the home page directly)
Result:
$ _ SERVER ["QUERY_STRING"] = ""
$ _ SERVER ["REQUEST_URI"] = "/"
$ _ SERVER ["SCRIPT_NAME"] = "/index. php"
$ _ SERVER ["PHP_SELF"] = "/index. php"
2, http://www.biuuu.com /? P = 222 (with query)
Result:
$ _ SERVER ["QUERY_STRING"] = "p = 222"
$ _ SERVER ["REQUEST_URI"] = "/? P = 222"
$ _ SERVER ["SCRIPT_NAME"] = "/index. php"
$ _ SERVER ["PHP_SELF"] = "/index. php"
3, http://www.biuuu.com/index.php? P = 222 & q = biuuu
Result:
$ _ SERVER ["QUERY_STRING"] = "p = 222 & q = biuuu"
$ _ SERVER ["REQUEST_URI"] = "/index. php? P = 222 & q = biuuu"
$ _ SERVER ["SCRIPT_NAME"] = "/index. php"
$ _ SERVER ["PHP_SELF"] = "/index. php"
$ _ SERVER ["QUERY_STRING"]: obtain the query statement. Which of the following statements can be obtained in the instance? Value after
$ _ SERVER ["REQUEST_URI"] gets the value after the http://www.biuuu.com, including/
$ _ SERVER ["SCRIPT_NAME"] obtains the path of the current script, for example, index. php.
$ _ SERVER ["PHP_SELF"] file name of the script currently being executed
To sum up, for QUERY_STRING, REQUEST_URI, SCRIPT_NAME, and PHP_SELF, an in-depth understanding will help us call these four values correctly in the $ _ SERVER function. Explain the differences between the four variables in the $ _ SERVER function: QUERY_STRING, REQUEST_URI, SCRIPT_NAME, and PHP_SELF.