How to concatenate multiple ternary operator in PH

问题:

I use ternary operators alot but I can't seem to stack multiple ternary operator inside each other.

I am aware that stacking multiple ternary operator would make the code less readable but in some case I would like to do it.

This is what I've tried so far :

$foo = 1;
$bar = ( $foo == 1 ) ? "1" : ( $foo == 2 ) ? "2" : "other";
echo $bar; // display 2 instead of 1

What is the correct syntax ?

回答1:

Those parenthesis are what I think is getting you.

Try

$foo = 1;
$bar = ($foo == 1) ? "1" : (($foo == 2)  ? "2" : "other");
echo $bar;

回答2:

The problem is that PHP, unlike all other languages, makes the conditional operator left associative. This breaks your code – which would be fine in other languages.

You need to use parentheses:

$bar = $foo == 1 ? "1" : ($foo == 2 ? "2" : "other");

(Notice that I’ve removed the other parentheses from your code; but these were correct, just redundant.)

回答3:

You need some parentheses around the right hand operand:

$foo = 1;
$bar = ( $foo == 1 ) ? "1" : (( $foo == 2 ) ? "2" : "other");
echo $bar;

PHP's interpreter is broken, and treats your line:

$bar = ( $foo == 1 ) ? "1" : ( $foo == 2 ) ? "2" : "other";

as

$bar = (( $foo == 1) ? "1" : ( $foo == 2)) ? "2" : "other";

and since that left hand expression evaluates as "true" the first operand of the remaining ternary operator ("2") is returned instead.

回答4:

You could write this correctly thus:

$bar = ($foo == 1) ? "1" : (($foo == 2) ? "2" : "other");

(i.e.: Simply embed the 'inner' ternary operator in parenthesis.)

However, I'd be really tempted not to do this, as it's about as readable as a particularly illegible thing that's been badly smudged - there's never any excuse for obfuscating code, and this borders on it.

回答5:

Put parenthesis around each inner ternary operator, this way operator priority is assured:

$bar = ( $foo == 1 ) ? "1" : (( $foo == 2 ) ? "2" : "other");

回答6:

Add the parenthesis:

$bar = ( $foo == 1 ) ? "1" : (( $foo == 2 ) ? "2" : "other");

回答7:

Just stack up the parenthesis, and you've got it:

$bar = ($foo==1? "1" : ($foo==2? "2" : "other"));

As an aside, if you've got many clauses, you should consider using a switch:

switch ( $bar ) {
  case 1:  echo "1";
  case 2:  echo "2";
  default: echo "other";
}

If the switch gets long, you can wrap it in a function.

回答8:

$foo = 1;
$bar = ( $foo == 1 ) ? "1" : (( $foo == 2 ) ? "2" : "other");
echo $bar;

Just use extra ( ) and it will work