What is the meaning of the "Use of undefined constant" notice in PHP? [duplicate]

This question already has answers here: What does the PHP error message "Notice: Use of undefined constant" mean? 开发者_运维知识库 (2 answers) Closed 9 years ago.

Notice: Use of undefined constant username - assumed 'username' in
/home/content/04/7195304/html/header.php on line 54

I get this when writing things like $_COOKIE[username] or $_POST[username].

Edit

So I've been playing around with the code, putting quotes in my POST, COOKIE, and GET's.. I still get the same thing!

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It means you likely forgot a $ in front of your variable name.

Edit You need to encapsulate your call in qoutes. I.e.

$_COOKIE["username"]

or

$_POST["username"]

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It probably means you forgot to put a $ in front of your username variable, so it's treating it like a constant instead of a variable.

You should post the code from that line for better help.

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You might as well try $_COOKIE['username'] or $_POST['username'], to access the associative arrays with a string.

Sorry, overlooked comment with same advice.