php - unusual ternary operation

Question

I was asked to perform this operation of ternary operator use:

$test='one';

echo $test == 'one' ? 'one' :  $test == 'two' ? 'two' : 'three';

Which prints two (checked using php).

I am still not sure about the logic for this. Please, can anybody tell me the logic for this.

Answer 1

Well, the ? and : have equal precedence, so PHP will parse left to right evaluating each bit in turn:

echo ($test == 'one' ? 'one' :  $test == 'two') ? 'two' : 'three';

First $test == 'one' returns true, so the first parens have value 'one'. Now the second ternary is evaluated like this:

'one' /*returned by first ternary*/ ? 'two' : 'three'

'one' is true (a non-empty string), so 'two' is the final result.