No Nested Ternary

The ternary operator is a compact version of a if then else structure. It is very convenient when the branching is needed but should be inline with the rest of the code.

<?php
print 'Result : '.( $success ? 'transaction succeded' : 'transaction failed');
?>

Ternary operators may be nested. This degrades very quickly the readability of the code.

<?php
print 'Result : '.( $success ? $christmas ? 'transaction success and you get a gift' : 'transaction success' : 'transaction failed');
?>

It must also be mentioned that ternary may not produce the expected result when nesting them. For example :

<?php

echo $foo ? 'a' : $bar ? 'b' : 'c';

?>

Here is the result for all values of $foo and $bar :

$foo	$bar	result
true	true	b
true	false	b
false	true	b
false	false	c

It is recommended to avoid nesting ternary operators.

Rule Details

Ternary operators are fine. Nesting them hurts.

The following code will raise a warning :

<?php

$foo ? 'a' : $bar ? 'b' : 'c';

$foo ?: $bar ? 'b' : 'c';

$foo ?: $bar ?: 'c';

?>

The following code will is legit :

<?php

$a = $bar ? 'b' : 'c';
$d = $foo ? 'a' : $b;

if ($foo) {
	$d = 'a';
} elseif ($bar) {
	$d = 'b';
} else {
	$d = 'c';
}

?>