corresponding nested ternary operator in php?

问题

I want to convert following if else condition to nested ternary operator.

if ($projectURL) {
    echo $projectURL;
} elseif ($project[\'project_url\']) {
    echo $project[\'project_url\'];
} else {
    echo $project[\'project_id\'];
}

I have written like following.

echo ($projectURL)?$projectURL:($project[\'project_url\'])?$project[\'project_url\']: $project[\'project_id\'];

But it is found as not working properly.Is this not a right way?

回答1:

Ternary operators are tricky thing in PHP, as they are left-associative (unlike all other languages, where it's right-associative). You will need to use parenthesis to tell PHP what you want exactly in this case:

echo ($projectURL ? $projectURL : ($project['project_url'] ? $project['project_url'] : $project['project_id']));

回答2:

As of php 7 we can use Null coalescing operator

echo $projectURL ?? $project['project_url'] ?? $project['project_id'];

来源：https://stackoverflow.com/questions/14728810/corresponding-nested-ternary-operator-in-php