PHP: The best way to check if 3 variables are identical?

Question

Forgive me if this is a common thing but I'm not sure how I should go about it.

I would like to see if three variables are identical to each other

I thought i could do this:

<?php
 if ($one == $two == $three) {
  echo "they all match.";
 } else {
  echo "one of these variables do not match."; 
 }
?>

But i guess that's not possible.

Is there a syntax for this? or do I have to check them individually/with && or || ?

I'm aware that checking them separately would give more accuracy (and is probably better practice) but for this particular situation it doesn't matter which one doesn't match.

Comes up commonly in interview questions : How to tell if a triangle is equilateral — basarat, Apr 15 '13 at 04:12

score 9 · Accepted Answer · answered Aug 03 '11 at 00:55

9

I would use:

if ( $one === $two && $two === $three )
    echo "they all match."
else
    echo "one of these variables do not match.";

#1 == #2 (no type coercion)
#2 == #3 (no type coercion)
∴ #1 == #2 == #3

answered Aug 03 '11 at 00:55

Jon Gauthier

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Thank you for the explanation at the bottom of your answer, I got it when you said it and had an 'Ah-ha!' moment, but you illustrated it wonderfully which will make it easier to remember. Thank you. (Also, fastest answer. Gratz. =) ) – Partack Aug 03 '11 at 01:04

score 7 · Answer 2 · answered Aug 03 '11 at 00:59

7

Here's an alternative solution that might be helpful. It will be particularly useful if your variables are already in an array.

$a = array($one, $two, $three);

if(count(array_unique($a)) == 1){
  // all match
}
else {
  // some items do not match
}

answered Aug 03 '11 at 00:59

maček

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Ooh, "array unique"? awesome. Thanks for that, it'll come in handy later on in my script =) – Partack Aug 03 '11 at 01:05

score 4 · Answer 3 · answered Aug 03 '11 at 00:56

4

You have you use &&. Fortunately, by the transitive property of ==, you only have to check two out of three :).

if ($one == $two && $two == $three) {
    echo "they all match.";
} else {
    echo "one of these variables do not match."; 
}

Want a "do what I mean" language? Use Python.

>>> a = 'foo'
>>> b = 'foo'
>>> c = 'foo'
>>> a == b == c
True

answered Aug 03 '11 at 00:56

Matt Ball

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hahaha, that last snippet looks fun. I'm going to learn python one of these days, just don't know when.. I've heard many good things about it ^__^ thanks for your quick response =) – Partack Aug 03 '11 at 01:01
3

Much `<3` for Python. Of course you can also do stuff like `x < y <= z` instead of `x < y and y <= z` as well. – Matt Ball Aug 03 '11 at 01:02

score 3 · Answer 4 · answered Aug 03 '11 at 00:57

3

Dont think you can do it simpler then:

if ($one == $two && $two == $three)

answered Aug 03 '11 at 00:57

Poul K. Sørensen

16,950
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Seems this is a common thing after all. haha. Thank you for your quick response =) – Partack Aug 03 '11 at 01:02

PHP: The best way to check if 3 variables are identical?

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