Your code is definitely correct and should work as expected, outputting 'title2'.
However, your condition isset($title1) && $title1 is not the same. This is more like the 'Elvis' operarator ?: checking for evaluation to boolean, except that the Elvis operator always returns a value (that might be null) and throws a notice on undefined operands. You would have to mute that by the @ operator.
Your if-else-construct is almost equivalent to
$title = @$title1 ?: @$title2 ?: @$title3;
The only difference is that $title here is assigned anyway while in your if-else-construct $title is left untouched when all operands are evaluated to false.
Be aware that muting by the @ operator also prevents critical errors to be shown, e.g. when using a function as operand.
An alternative is to define your own function. Arguments by value throw a notice on unset variables as well, however, arguments by reference do not. You can design a variadic function taking references:
function firstNonEmpty(&...$variableRefs)
{
$v = null; // ensure declaration since loop might not interate at all
foreach ($variableRefs as $v)
if($v) break;
return $v ?: null; // we want null even if last value is like false
}
$c = 'value not considered to be empty';
$v = firstNonEmpty($a, $b, $c, $d);
Arguments by reference do not accept literals, thus appending some as default argument will not work. However, you can simply use the null-coalescing operator ?? in this case. There is fairly no use-case to add more than one default literal since you know at developtment time whether or not a literal evalualtes to false.
$v = firstNonEmpty($a, $b, $c, $d, 'default') ; // does NOT work
$v = firstNonEmpty($a, $b, $c, $d) ?? 'default'; // DOES work
// One strange thing of PHP is that
$v = firstNonEmpty($a, ...[0, null, '', 'non-empty']); // DOES work as well
The latter literally creates an array of literals on the fly and references the destructed items. The only thinkable use-case having more than one literal would be generated code by eval.
