我可以使用逻辑OR || 在PHP变量声明？

Question

This code works:

$foo = getFoo();
if (!$foo) $foo = getBar();
if (!$foo) $foo = getJiggy();
if (!$foo) $foo = getWithIt();

I thought I'd seen somewhere a simplification of it with logical operators:

$foo = (getFoo() || getBar() || getJiggy() || ...);

I figured that the first true statement would get passed, but instead, it's just setting $foo to boolean true instead of the return value of getFoo(), getBar(), etc.

Is there a simplification like what I'm thinking of?

Answer 1

For JavaScript, foo = bar || baz; is a commonly used expression, as the || operator has a coalescing behavior.

PHP does not have this behavior with regard to the || operator, which returns a boolean value. As such, the more verbose code you originally posted:

$foo = getFoo();
if (!$foo) $foo = getBar();
if (!$foo) $foo = getJiggy();
if (!$foo) $foo = getWithIt();

is your most readable, and preferable option.

PHP 5.3 has a shorthand version of the ternary operator, which acts as a coalescing operator:

Since PHP 5.3, it is possible to leave out the middle part of the ternary operator. Expression expr1 ?: expr3 returns expr1 if expr1 evaluates to TRUE, and expr3 otherwise.

This would allow you to use:

$foo = getFoo() ?: getBar() ?: getJiggy() ?: getWithIt();

However, that assumes you don't have to worry about compatibility.