我可以使用逻辑OR || 在PHP变量声明？

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?

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.

You can use nested ternary operator. Something like:

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

Try

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

You can try

$foo = getFoo() or $foo = getBar() or $foo = getJiggy() or $foo = getWithIt();
var_dump($foo);

Output

string 'Stop Here' (length=9)

Function Used

function getFoo() {
    return false;
}

function getBar() {
    return false;
}

function getJiggy() {
    return "Stop Here";
}

function getWithIt() {
    return "Hello World";
}

You can use the weaker-precedence or and build up a condition+assignment chain like this:

    $foo = getFoo()
OR  $foo = getBar()
OR  $foo = getJiggy()
OR  $foo = getWithIt();

For readability and easing others to understand such operator misuse, spacing is essential.

if you really want to rewrite your code, you could use call_user_func, but it's not a very elegant solution:

$foo = false;//best declare vars before using them, to avoid warnings in strict mode
$functions = array('getFoo', 'getBar','getJiggy','getWithIt');
while(!$foo && $func = array_shift($functions))
{
    $foo = call_user_func($func,null);//replace null with optional parameters
}

But as you can see, this would be even less maintainable...