CODEWITHSUNDEEP
phpif-statement
sergiu reznicencu
sergiu reznicencu

Reputation: 1039

Function executing order in an if statement php

I want to make a function for a "secure" php page that will check the token(the one passed by post and the one from the session).
      But I don't want to write two if statements like this:

function CheckToken(){
    if(isset($_POST['token']) && isset($_SESSION['token']))
        if($_POST['token']==$_SESSION['token']) return true;

    return false;
}

Can I do something like this(?):

function CheckToken(){
    if(isset($_POST['token']) && isset($_SESSION['token']) && $_POST['token']==$_SESSION['token']) return true;
    return false;
}

     Here's all about the order in which those functions are executed (when using the and operator).So if you're using the AND operand then if the first conditions is false don't evaluate the second. I remember that vb.net had a solution to this problem(evaluating only the first function-if it is false don't evaluate the second one).
     So, is it safe to put everything on a single line(like I did in the second example)?

Upvotes: 1

Views: 1182

Answers (2)

Lionel Chan
Lionel Chan

Reputation: 8059

PHP does the same thing as the usual if statement evaluation in other major languages, that is, check from left to right.

So if you have

if (cond1 && cond2 && cond3)

Scenario 1:
If cond1 is true, it will then execute cond2, and then cond3.
Sample: https://3v4l.org/Ap9SQ

Scenario 2:
If let's say cond2 is false, then cond3 will be ignored.
Sample: https://3v4l.org/u9P4O

Same goes to OR

if (cond1 || cond2 || cond3)

If cond1 is true, cond2 and cond3 will be skipped.
Sample: https://3v4l.org/ZAZcD

So since your function is just returning true or false, you can even simplify it to something like this:

function CheckToken() {
    return isset($_POST['token']) &&
           isset($_SESSION['token']) &&
           $_POST['token'] == $_SESSION['token'];
}

Split lines for readability. Also checkout isset manual as you can pass in multiple variables for empty checking.

Upvotes: 3

Wolfsmash
Wolfsmash

Reputation: 119

Yes, there really is no difference to changing the order like that. It is perfectly safe, because all it's doing is changing the look of the script while the execution is the EXACT same.

It would be best to do the second option.

Upvotes: 1

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