Define/set PHP variable

Question

I often get PHP errors about a variable not defined. I'm also wondering what is best practice for setting session variables. Currently I'm doing this:

session_start();

if (!isset($_SESSION["myVar"]))
  $_SESSION["myVar"] = "";

But this seems untidy to me. I know there is a PHP unset function, but what is the equivalent to simply set/define a variable into existence, without setting an initial value?

For now, a session var, but I also wonder the best way to be defining variables in PHP. — Daniel Williams
– Daniel Williams, Commented Jan 1, 2018 at 22:18

jack · Accepted Answer · 2018-01-01 22:30:38Z

2

Php has dynamic variable allocation and typing. When a variable is first referenced within a program, memory is allocated for its use.

Meaning that unless you don't assign a value, a variable can't be declared, like say, in java.

Best way how to make sure you "declare" all your variables?

Assign them to null or empty string at the beginning of each function / method.

About session variables, I'd apply the same logic.

edited Jan 1, 2018 at 22:30

answered Jan 1, 2018 at 22:18

jack

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2 Comments

Daniel Williams Over a year ago

So in this case $_SESSION["myVar"] = ""; would be correct?

jack Over a year ago

Yes. If you think your variable type might change in runtime, then maybe assign as null in the beginning.

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