So I understand this - and comparing/checking values. However, I was messing about and noticed the outcome for all my tests were the same - some of which I was taught (a) didn't work or (b) was incorrect.
Note, I'm running PHP7. Okay, to my point. I was able to achieve the same outcome checking if a single value equals one of multiple options...
These work...why? Def not the way I learned.
if ($status == 'in-progress' || 'in-review')
// and even
if ($status == ('in-progress' || 'in-review')) // kind of similar to ASP.NET Razor
I normally would repeat the check, like so: if($stat == 'a' || $stat == 'b') or even in_array() which is essentially the same thing.
Is the first examples, correct? If not, why is it working? Or is this something frowned upon and not practiced - or maybe even something new?
First off to make it clear == has a higher precedence than ||. This means your two if statements look like this:
if (($status == 'in-progress') || 'in-review')
if ($status == ('in-progress' || 'in-review'))
Now for your first if statement regardless what value $status has and what the outcome of ($status == 'in-progress') is, since you have an OR in it and after it 'in-review' your if statement will always be true, since a non empty string is a truthy value.
For your second statement, this part ('in-progress' || 'in-review') comes literally down to TRUE || TRUE, which evaluates to TRUE. Now $status just needs to hold a truthy value and the if statement will be true.
No, that code will never work. || has a lower precedence than ==, so you're comparing $status against the first value, then boolean || "or" the other value
if (($status == 'foo') || ('bar'))
You have to compare the values individually:
if (($status == 'foo') || ($status == 'bar'))
And this gets tedious for many values. A quick hack is to use an array:
if (in_array($status, array('foo', 'bar', 'baz', 'qux', 'etc...')))
Related
This question already has an answer here:
How to get OR(||) and AND (&&) statements to work together? PHP
(1 answer)
Closed 3 years ago.
I have an "if" statement I would like to write with multiple comparison operators of the "&&" and "||" type. I am not entirely sure if it will perform the way I am thinking it should. Here is an example of what I am trying to do.
if($alpha == "FF" && $bravo == "3sh" || $charlie == "6sh")
{
printf($alpha);
}
What I expect is that $alpha MUST equal "FF" in order for this to execute.
What I also expect is at least one of the other two conditions must be met in order to execute.
What I am concerned about is the code ignoring the first two conditions and executing the code because the last condition is met.
You can create wrap conditions accordingly as below:
if($alpha == "FF" && ($bravo == "3sh" || $charlie == "6sh"))
{
printf($alpha);
}
So here, $alpha == "FF" should have to be true. And either one condition should be true in between on braces. Hope it helps you.
It may be helpful to look into Boolean logic a litte more, but for your particular situation what you are trying to do is:
if($alpha == "FF" && ($bravo == "3sh" || $charlie == "6sh"))
{
printf($alpha);
}
Essentially, you say
$alpha == "FF" must be true AND
($bravo == "3sh" || $charlie == "6sh") must be true
- i.e., either $bravo == "3sh" OR $charlie == "6sh"
I found an example php assignment statement online which maybe resembles a tertary conditional condensed statement, but not quite. Does anyone have insight as to how to read this assignment statement?
$access = $access || $note->uid == $user->uid && user_access('note resource view own notes');
My first guess was "assign to access whatever is in access, or if empty, whether uid values are equal and'd with the return of user_access." But I get the feeling that is not correct, as it seems illogical.
First have a look at the Operator Precedence
== comes before && comes before || comes before =
Thus your statement is more clear with adding the following parentheses:
$access = (
$access
||
(
($note->uid == $user->uid)
&&
user_access('note')
)
);
assign to access whatever is in access, or if empty,
Not quite: assign to $access the value true* when $access already evaluates to true (true, 1, "some string" etc), or
whether uid values are equal and'd with the return of user_access
Correct
And otherwise assign false. After this statement $access is always either true or false, even when $access === 'yes' before.
Note*: || and && are boolean operators, only capable of 'returning' true or false
I had this exact type of statement in a library way back, and it's basically an elaborate (or maybe just badly-styled?) null-check. Because PHP uses short circuit evaluation, the right-hand side of the or-expression will not evaluate if the left hand one was null.
I am trying to do this in a single IF statement to avoid having duplicated code, I would like to know if it is possible to do what I want to do.
I originally had this code to run code on all categories that doesn't equal '15', Now I need it to not apply to categories 15 and 57.
Original code:
if ($level==1 && $category_id!=15){
New code (the general idea):
if ($level==1 && ($category_id!=15 || $category_id!=57)){
Edit: If downvoting, please explain why. I have tested the code above and it always returns false.
The following code means that if will be true when $level equals to 1 and $category_id doesn't equal to none of 15, 57.
if ($level == 1 && !in_array($category_id, array(15, 57)))
Have a look here: in_array
It should be:
if ($level==1 && $category_id!=15 && $category_id!=57){
You can just use multiple and criteria:
if ($level==1 && $category_id!=15 && $category_id!=57){
The reason your current code fails (it will always return true when $level==1) is because $category_id can never be both values.
let $category_id ==15 then the left side of the condition ($category_id!=15 || $category_id!=57) will evaluate to false (15 != 15) == false so the right side will be evaluated (15 != 57) == true causing the overall statement to evaluate to true.
let $category_id ==57 then the left side of the condition ($category_id!=15 || $category_id!=57) will evaluate to true (57 != 15) == true so the right side is never evaluated, causing the overall statement to evaluate to true.
I am confuse with bellow code:
Fist code that is not working:
if ($_SESSION['userType'] != 'A' || $_SESSION['userType'] != 'S')
{
redirect('dashboard.php');
}
Second code that is working:
if (!($_SESSION['userType'] == 'A' || $_SESSION['userType'] == 'S'))
{
redirect('dashboard.php');
}
What is difference between both code?
I know you already have six answers to your question, but none of them uses plain English, so I'll make an attempt myself as well.
Let's look at this code step by step, splitting it up into smaller portions, and explaining each step exactly.
Code that isn't working
First you have this row:
if ($_SESSION['userType'] != 'A' || $_SESSION['userType'] != 'S')
Instead of looking at the full if clause already, let's divide it into two parts:
if ($_SESSION['userType'] != 'A')
if ($_SESSION['userType'] != 'S')
The first part will trigger any time that $_SESSION['userType'] is any value other than A.
The second part will trigger any time that $_SESSION['userType'] is any value other than S.
Now, you've joined them both together with an "or" operator, so that it's enough that one of them is true for the if clause to trigger. Let's see what happens when we try it out.
We set $_SESSION['userType'] to 'B' and go into the if clause. The first thing that happens is that PHP looks at the first part, if ($_SESSION['userType'] != 'A'), and finds that 'B' != 'A'. It doesn't need to go to the second part, because it already found that one of the parts of the if statement is true, and so it decides that the full if statement must also be true.
We set $_SESSION['userType'] to 'A' and go into the if clause. The first thing that happens is that PHP looks at the first part, if ($_SESSION['userType'] != 'A'), and finds that 'A' == 'A', so the first part is false. It then goes on to the second part, which is if ($_SESSION['userType'] != 'S'), and finds that 'A' != 'S'. Since this means that one of the parts of the if statement is true, it again decides that the full if statement must also be true.
Now notice what this means. Even if you send an 'A' to the if clause, it will still trigger because of the second part. And if you were to send an 'S', it will trigger because of the first part. So essentially, the full first if statement will trigger regardless of what $_SESSION['userType'] is set to. It's a tautology - it's always true.
Code that is working
This is your full if statement:
if (!($_SESSION['userType'] == 'A' || $_SESSION['userType'] == 'S'))
Let's ignore the ! for now, and divide it into the two parts of the or operator.
if ($_SESSION['userType'] == 'A')
if ($_SESSION['userType'] == 'S')
Notice that this is the logical opposite of the code you had that didn't work. The first row means "only accept an 'A'" and the second means "only accept an 'S'". So this code will trigger only if you give it either an 'A', or an 'S'.
Now, what happens if you put an ! in front of the whole thing, like you did?
The ! operator simply reverses whatever it is put in front of. So this changes the meaning from "either A or S" to "neither A nor S".
Summary
Your first example comes down to "any value whatsoever".
Your second example comes down to "any value, but not A, and also not S".
If you want to learn more of basic logic, I suggest looking at De Morgan's laws, as you were linked to in an above comment. This will give you an understanding of how and and or fits together.
Not...quite.
If I remember boolean logic correctly, the fault lies in order of operations.
if ($_SESSION['userType'] != 'A' || $_SESSION['userType'] != 'S') {
if userType equals A, this will not work...since the first operation is to check that it is not equal to A and ORs are left to right...so if the first is not true, the entire statement is false.
Your second approach translates to:
if (!($_SESSION['userType'] == 'A' || $_SESSION['userType'] == 'S'))
{
redirect('dashboard.php');
}
IF NOT userType equals A OR userType equals S which is why it works as you desire it to.
Try
if ($_SESSION['userType'] != 'A' && $_SESSION['userType'] != 'S')) {
which means IF userType is not A and userType is not S
I think that will give you what you are probably looking for. IE Only do what is in the loop if the userType is neither A, nor S.
if ($_SESSION['userType'] != 'A' || $_SESSION['userType'] != 'S') {
is more or less equivalent to
if (!($_SESSION['userType'] == 'A' && $_SESSION['userType'] == 'S')) {
first code that is not working
if ($_SESSION['userType'] != 'A' || $_SESSION['userType'] != 'S')
{
redirect('dashboard.php');
}
lets simplyfy it as under:
if (true || true) //the condition will be true or vice versa
{
redirect('dashboard.php');
}
Second code that is working:
if (!($_SESSION['userType'] == 'A' || $_SESSION['userType'] == 'S'))
{
redirect('dashboard.php');
}
and the simplified version:
if (!(true || true)) same as if (!(true)) //i.e. false or vice versa
{
redirect('dashboard.php');
}
so basically one is true and the other is false or vice versa so thats why they are acting diffrenetly.
I have an if statement that I want to control with having one field needing input and they have to pick one of the other 2 choices.
if(test1 && test || test3){
//Something here
}
Should I do it like this:
if(test1 && (test2 || test3)){
//do stuff
}
How would I go about doing this. I can't wrap my head around the logic...
if ($requiredField && ($optional1 || $optional2)) {
/* Do something */
}
For the /* Do something */ bit of code to be executed, the if statement has to evaluate to TRUE.
This means, that $requiredField must be TRUE, and so must be ($optional1 || $optional2).
For $requiredField to be TRUE, it just needs to be filled in - and for the second part: ($optional1 || $optional2) either optional1 or optional2 would do it.
Edit:
After rereading the question, it seems that I might have misunderstood you. If the user must enter one specific piece of information, and must choose only one (not both) out of two options - then the following should be used.
if ($requiredField && ($optional1 ^ $optional2)) {
/* Do something */
}
This means that $optional1 or $optional2 must be filled out - but not both of them.
From the sound of it, you want the latter:
if ($test1 && ($test2 || $test3)){
//do stuff
}
Think of it as two conditions needing to be met. This gives you those two conditions. The second condition just happens to be another condition. The first option you posted, however, is quite the opposite as it can allow execution if just $test3 is true
test1 && (test2 || test3) is very easy to understand from the first place - Choose test1 && (test2 || test3) means one the last two. Very clear.
test1 && test || test3 - doesn't seem to be correct:
test1 = false
test2 = false
test3 = true
false && false || true = true
doesn't actually fit your criteria.
... they have to pick one of the other 2 choices
I'm just throwing a guess out here. If you really want to ensure that one, but only one of the two other options are selected, then you need xor:
if ($required AND ($and_either XOR $or_other)) {
You can have 'nested' if statements withing a single if statement, with additional parenthesis.
if(test1 && (test2 || test3)){
//do stuff
}
Your logic is right but your sintax isnt, you should compare the values of the variables as show, or simply ignore them as saying you are trying to compare them as they are TRUE.
$test1=true;
$test2=true;
$test3=false;
if($test1==true && ($test2==true || $test3==true){ echo "YES";}
This will output YES.