PHP: Assign multiple variables in if statement

Question

I don't seem to be able to assign multiple variables in an "if" statement. The following code:

<?php

function a ($var)
{
    if ($var == 1)
    {
        return 'foo';
    }

    return false;
}

function b ($var)
{
    if ($var == 1)
    {
        return 'bar';
    }

    return false;
}

if ($result1 = a(1) && $result2 = b(1))
{
    echo $result1 . ' ' . $result2;
}

?>

Returns "1 bar" rather than "foo bar". If I remove the second condition/assignment it returns "foo".

Is there a way to assign multiple variables in an "if" statement or are we limited to just one?

This is a very bad idea. What if you put an 'or' condition between two assignments? IF (e=mc^2 or E=Mc^2) ... Did the second assignment execute? — Guy Gordon
– Guy Gordon, Commented Sep 21, 2017 at 12:37

marmeladze · Accepted Answer · 2022-07-31 11:06:22Z

5

This is all about operator precedence

<?php

function a ($var)
{
    if ($var == 1)
    {
        return 'foo';
    }

    return false;
}

function b ($var)
{
    if ($var == 1)
    {
        return 'bar';
    }

    return false;
}

if (($result1 = a(1)) && ($result2 = b(1)))
{
    echo $result1 . ' ' . $result2;
}

?>

https://repl.it/IQcU

UPDATE

assignment operator = is right-asscoiative, that means, evaluation of operand on rhs has precedence over the lhs operand.

thus,

$result1 = a(1) && $result2 = b(1)

is equivalent of,

$result1 = (a(1) && $result2 = b(1))

which evaluates

$result1 = ("foo" && [other valild assignment] )

which will result that,

$result1 becomes true

and echo true/string value of boolean true (strval(true)) outputs/is 1

you can also check that revision, https://repl.it/IQcU/1

to see that below statement

$result1 = a(1) && $result2 = b(1)

is equivalent of this one.

 $result1 = (a(1) && $result2 = b(1))

edited Jul 31, 2022 at 11:06

answered May 25, 2017 at 4:35

marmeladze

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2 Comments

Death-is-the-real-truth Over a year ago

correct.+1.But need to add more explanation regarding why 1 bar is coming?

Bob Meador Over a year ago

Aha. Can't believe I never came across this before. Normally I'm either assigning just a single value in the if condition or doing multiple comparisons ($a == 'foo'), which apparently do not associate across && and similar structures. I thought && was sort of a condition separator but apparently when doing assignment it is not. Thanks!

Death-is-the-real-truth · Accepted Answer · 2017-05-25 20:10:31Z

4

Need to add parentheses() in each assignment like below:-

if (($result1 = a(1)) && ($result2 = b(1)))
{
    echo $result1 . ' ' . $result2;
}

Output:- https://eval.in/804770

Correct explanation is given by @marmeladze here:-

Why 1 bar is coming through OP's code

edited May 25, 2017 at 20:10

answered May 25, 2017 at 4:35

Death-is-the-real-truth

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Comments

Abishek V Ashok · Accepted Answer · 2017-05-25 04:40:00Z

1

The last if statements need some brackets, it should have been:

if (($result1 = a(1)) && ($result2 = b(1)))
{
     echo $result1 . ' ' . $result2;
}

This ensures that things in the bracket are executed first and it will help.

answered May 25, 2017 at 4:40

Abishek V Ashok

5233 silver badges17 bronze badges

2 Comments

Death-is-the-real-truth Over a year ago

correct.+1.But need to add more explanation regarding why 1 bar is coming?

Abishek V Ashok Over a year ago

Things in the bracket are executed first. Without them it would have been: if ($result1 = a(1) && $result2 = b(1)) resulting in non assignment of the second variable.

Death-is-the-real-truth · Accepted Answer · 2017-05-25 07:00:48Z

0

You have to add == to check a condition.

Try this,

if ($result1 == a(1) && $result2 == b(1))
{
    echo $result1 . ' ' . $result2;
}

Checked with belo example

<?php 

function a ($var)
{
    if ($var == 1)
    {
        return 1;
    }

    return false;
}

function b ($var)
{
    if ($var == 1)
    {
        return 2;
    }

    return false;
}

if (1 == a(1) && 2 == b(1))
{
    echo 'success';
}
?>

edited May 25, 2017 at 7:00

Death-is-the-real-truth

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answered May 25, 2017 at 5:01

Deepak M

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1 Comment

Death-is-the-real-truth Over a year ago

I don't think it's anyhow solving problem of OP or giving him a clue why 1 bar is coming in his case?

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