Kapil Sharma Kapil Sharma - 3 months ago 9x
PHP Question

Ternary operator left associativity

In the PHP manual, I find the following 'user contributed note' under "Operators".

Note that in php the ternary operator ?: has a left associativity unlike in C and C++ where it has right associativity.

You cannot write code like this (as you may have accustomed to in C/C++):

$a = 2;
echo (
$a == 1 ? 'one' :
$a == 2 ? 'two' :
$a == 3 ? 'three' :
$a == 4 ? 'four' : 'other');
echo "\n";
// prints 'four'

I actually try it and it really prints
. However I could not understand the reason behind it and still feel it should print

Can someone please explain what is happening here and why it is printing 'four'?


Because your whole expression evaluates as if it was (......) ? 'four' : 'other'. Since the first element is probably something truthy, it gives you 'four'. In saner languages, where ?: has right associativity, the whole expression evaluates as if it was $a == 1 ? 'one' : (......), where if $a is not 1, you go on to test other things.