Difference between $a == 1 and 1 == $a

Question

I have seen multiple examples of such comparison, some other example ( from wordpress core):

if ( '' != $qv['subpost'] )
            $qv['attachment'] = $qv['subpost'];

Is code above same as:

if ( $qv['subpost'] != '' )
            $qv['attachment'] = $qv['subpost'];

or they are different in functionality?

Two kinds of programmers there are; those who Yoda and those who don't. — Ja͢ck, Oct 02 '14 at 14:20
Some people prefer Yoda programming (it requires a different mindset but removes the problem of having one = when two should be required) — Ed Heal, Oct 02 '14 at 14:22
Of course, in this particular example Yoda style makes no sense at all because it uses `!=` and not `==`. — Ja͢ck, Oct 02 '14 at 14:25
oh interesting stuff. It really is Yoda programming. Thanks everyone for infos — Zack Westwater, Oct 02 '14 at 14:31

score 5 · Accepted Answer · answered Oct 02 '14 at 14:25

Some people prefer the constant == variable option, as it'll cause fatal errors if you accidentally type a = and try to do assignment:

e.g.

$a = 'foo';  // assigns 'foo' to $a
$a == 'foo'; // tests for equality
'foo' == $a // tests for equality
'foo' = $a // syntax error - assigning value to a string constant

But functionally, otherwise, there's no difference between both versions. a == b is fully equivalent to b == a.

SeanWM · Answer 2 · 2014-10-02T14:25:46.213

0

Yes, they do the same thing. It checks to see if $qv['subpost'] contains a value in both examples. No difference at all unless you're Yoda.

edited Oct 02 '14 at 14:25

answered Oct 02 '14 at 14:20

SeanWM

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score 0 · Answer 3 · answered Oct 02 '14 at 14:20

0

There is no difference.

(A == B) == (B == A)

The only thing that someone can put the value first is the readability, for example:

if ( 'APPLE' == $var ) {

} else if ('BANANA' == $var) {

}

answered Oct 02 '14 at 14:20

hsz

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score 0 · Answer 4 · answered Oct 02 '14 at 14:21

There is no functional difference. You are comparing equality, and they will either be equal or not, no matter what side of the operator the values are on.

This question comes down to code style. Personally, when comparing against static values I prefer to always have the variable on the left. Others disagree. Use whatever style is in place in the project you're working on.

Difference between $a == 1 and 1 == $a

4 Answers4