I am trying to integrate a website from a partner of my company, and I running into this line here:
header("Location: field/index.php", overwrite);
I browsed the PHP manual of header() function, but can't find a parameter called overwrite.
Can someone give me any clue?
The second parameter (replace) means the same thing as overwrite. If you see the line:
header("Location: field/index.php", overwrite);
That is most likely not valid (it is technically valid if overwrite is a constant). It should be:
header("Location: field/index.php", true);
overwrite (without a dollar sign) works (yet generates a "Notice: Use of undefined constant") because if undefined, it becomes the string 'overwrite'. This string casts to Boolean true. In any case, the default for the function is true, so it should not be necessary.
It (overwrite) could be a constant, for example
define('overwrite', true);
header("Location: field/index.php", overwrite);
In this case overwrite represents Boolean true and which is being used to replace a previous header.
Though, constants should be declared using uppercase letters but it doesn't throw any errors if someone uses lowercase letters instead. Recommended way to define a constant is
defined('OVERWRITE') or define('OVERWRITE', TRUE);
It's worth mentioning that, any constant defined this way is available globally, throughout the script/application and basically developers define constants at the very beginning of script or an application and it could be defined in a different file (which is included/executed on start up) so, you may don't see it in the current script.
There are three parameters for PHP header():
"Location: field/index.php" here)http_response_code: Used to force the HTTP response codeFrom the documentation:
The optional replace parameter indicates whether the header should replace a previous similar header [...] By default it will replace
The overwrite value in your code is invalid, because it is an unquoted string where a boolean value should be. Using header("Location: field/index.php", true); is correct, but because true is default, you only need header("Location: field/index.php").
https://www.php.net/manual/en/function.header.php
The php site is good for this kind of question. The second param just tells it whether or not to "overwrite" (replace) a value that has already been set.
Note that the value passed into the function doesn't necessarily have anything to do with the name of the parameter. They are simply used in order. Here, overwrite must be a variable set somewhere else although it's surprising it doesn't have the typical $ in front of it marking it as a variable in PHP. The variable overwrite is evaluated and its value is passed as the second parameter in the header function.
$ in PHP. Without the $ it is a constant if such a constant is defined. Otherwise it is a warning and the string literal "overwrite".