运算符＆lt; =＆gt;比较对象？

时间：2016-03-27 11:53:53

标签： php php-7 spaceship-operator

在RFC中给出了这个例子：

// only values are compared
$a = (object) ["a" => "b"]; 
$b = (object) ["b" => "b"]; 
echo $a <=> $b; // 0

但是当我执行它时，我输出1作为输出：

$a = (object) ["a" => "b"];
$b = (object) ["b" => "b"];
echo $a <=> $b; //1

我现在不明白＆lt; =＆gt;比较对象？在RFC中，它表示仅通过值进行比较。

P.S。我在流浪汉下使用PHP 7.0.4-6 + deb.sury.org~trusty + 1（cli）（NTS）

UPD：

php > echo (object)["b"=>"b"] <=> (object)["b"=>"b"];
0
php > echo (object)["b"=>"b"] <=> (object)["a"=>"b"];
1
php > echo (object)["a"=>"b"] <=> (object)["b"=>"b"];
1

2 个答案:

答案 0 :(得分：4)

在阅读RFC时，我们发现它与自身相矛盾：

  

添加新运算符（expr）＆lt; =＆gt; （expr），如果两个操作数相等则返回0，如果左边更大则返回1，如果右边更大则返回-1。 使用与现有比较运算符完全相同的比较规则：＆lt;，＆lt; =，==，＆gt; =和＆gt;。 （有关详细信息，请参阅手册）

注意：请参阅==，这意味着太空船运营商进行了松散的比较。

稍后在示例中：

// only values are compared
$a = (object) ["a" => "b"]; 
$b = (object) ["b" => "b"]; 
echo $a  $b; // 0

太空船运营商只是运营商<，==和>的组合。它根据评估结果给出各自的返回值：

operator(s):   <  =  >
return value: -1  0  1

现在arrays和objects有点复杂types。要了解<=> PHP太空船运营商的作用，我们需要查看并了解<，==和>如何适用于数组和对象。

让我们看看每种类型的比较运算符<，>，==。首先，我们将查看<和>，然后我们会查看==。

数组比较运算符

现在，数组<和>已记录在案here：

┌───────────┬───────────┬──────────────────────────────────────────────────┐
│ type of   │ type of   │                                                  │
│ Operand 1 │ Operand 2 │ Result                                           │
├───────────┼───────────┼──────────────────────────────────────────────────┤
│ array     │ array     │ Array with fewer members is smaller,             │
│           │           │ if key from operand 1 is not found in operand 2  │
│           │           │ then arrays are uncomparable,                    │
│           │           │ otherwise - compare value by value               │
└───────────┴───────────┴──────────────────────────────────────────────────┘

这也可以由code编写和表示：

  

示例＃2标准数组比较的转录

<?php
// Arrays are compared like this with standard comparison operators
function standard_array_compare($op1, $op2)
{
    if (count($op1) < count($op2)) {
        return -1; // $op1 < $op2
    } elseif (count($op1) > count($op2)) {
        return 1; // $op1 > $op2
    }
    foreach ($op1 as $key => $val) {
        if (!array_key_exists($key, $op2)) {
            return null; // uncomparable
        } elseif ($val < $op2[$key]) {
            return -1;
        } elseif ($val > $op2[$key]) {
            return 1;
        }
    }
    return 0; // $op1 == $op2
}
?>

我们可以通过一些测试轻松测试。使用methods like in math并且始终只更改一件事，因此我们可以确保在这里正确无误：

/**
/*
/* Testing operators: < and >
/*
 */ 

//Test case
//Variations: amount, values and keys (order)
//Test count: 9
//    Failed: 0
//    Passed: 9    
{
    //Test case 1.1
    $a = [1];
    $b = [1];

    //Passed
    var_dump("Same amount of elements, keys and values: " . "'<' -> " . bool2str($a < $b) . " '>' -> " . bool2str($a > $b));
   
    //Test case 1.2
    $a = [1];
    $b = [1, 1];

    //Passed
    var_dump("NOT same amount of elements, but same values: " . "'<' -> " . bool2str($a < $b) . " '>' -> " . bool2str($a > $b));

    //Test case 1.3 
    $a = [10];
    $b = [1, 1];

    //Passed
    var_dump("NOT same amount of elements nor values: " . "'<' -> " . bool2str($a < $b) . " '>' -> " . bool2str($a > $b));
    
    //Test case 1.4
    $a = [1 => 1];
    $b = [10 => 1];

    //Passed
    var_dump("Same amount of element and values, NOT same keys: " . "'<' -> " . bool2str($a < $b) . " '>' -> " . bool2str($a > $b));

    //Test case 1.5
    $a = [10];
    $b = [1];

    //Passed
    var_dump("Same amount of elements and keys, NOT same values: " . "'<' -> " . bool2str($a < $b) . " '>' -> " . bool2str($a > $b));
    
    //Test case 1.6
    $a = [1 => 1, 2 => 1];
    $b = [2 => 1, 1 => 1];

    //Passed
    var_dump("Same amount of elements and keys in different order: " . "'<' -> " . bool2str($a < $b) . " '>' -> " . bool2str($a > $b));
    
    //Test case 1.7
    $a = [1 => 1, 2 => 5];
    $b = [2 => 5];

    //Passed
    var_dump("Same values, NOT same amount of elements nor keys: " . "'<' -> " . bool2str($a < $b) . " '>' -> " . bool2str($a > $b));
    
    //Test case 1.8
    $a = [10 => 1];
    $b = [1 => 10];

    //Passed
    var_dump("NOT same keys nor values: " . "'<' -> " . bool2str($a < $b) . " '>' -> " . bool2str($a > $b));
    
    //Test case 1.9
    $a = [1 => 1, 2 => 1];
    $b = [2 => 10, 1 => 1];

    //Passed
    var_dump("Same amount of elements and values, NOT same keys nor order: " . "'<' -> " . bool2str($a < $b) . " '>' -> " . bool2str($a > $b));
    
}


echo PHP_EOL . PHP_EOL . PHP_EOL;  //Test case separator

/**
/*
/* Test case end
/*
 */

//NULL, TRUE, FALSE 2 str func
function bool2str($v){if($v === NULL)return "NULL";elseif($v === FALSE)return "FALSE";elseif($v === TRUE)return "TRUE";else return "UNEXPECTED: '$v'";}

对于相等/同一性运算符==和===，我们找到了数组here的文档：

┌───────────┬──────────┬──────────────────────────────────────────────────┐
│ Example   │ Name     │ Result                                           │
├───────────┼──────────┼──────────────────────────────────────────────────┤
│ $a == $b  │ Equality │ TRUE if $a and $b have the same key/value pairs. │
│ $a === $b │ Identity │ TRUE if $a and $b have the same key/value pairs  │
│           │          │ in the same order and of the same types.         │
└───────────┴──────────┴──────────────────────────────────────────────────┘

和以前一样，我们可以使用一些测试代码来测试它：

/**
/*
/* Testing operators: == and ===
/*
 */ 

//Test case
//Variations: amount, values and keys (order)
//Test count: 5
//    Failed: 0
//    Passed: 5     
{
    //Test case 2.1
    $a = [1];
    $b = [1];

    //Passed
    var_dump("Same amount of elements, values and keys: " . "'==' -> " . bool2str($a == $b) . " '===' -> " . bool2str($a === $b));
   
    //Test case 2.2
    $a = [1];
    $b = [10, 1];

    //Passed
    var_dump("NOT same amount of elements, but same values: " . "'==' -> " . bool2str($a == $b) . " '===' -> " . bool2str($a === $b));

    //Test case 2.3
    $a = [10];
    $b = [1];

    //Passed
    var_dump("Same amount of elements, but not values: " . "'==' -> " . bool2str($a == $b) . " '===' -> " . bool2str($a === $b));
    
    //Test case 2.4
    $a = [1 => 1];
    $b = [10 => 1];

    //Passed
    var_dump("Same amount of elements and values, but not keys: " . "'==' -> " . bool2str($a == $b) . " '===' -> " . bool2str($a === $b));
    
    //Test case 2.5
    $a = [1 => 1, 2 => 2];
    $b = [2 => 2, 1 => 1];

    //Passed
    var_dump("Same amount of elements, key and values, but different order: " . "'==' -> " . bool2str($a == $b) . " '===' -> " . bool2str($a === $b));
    
}


echo PHP_EOL . PHP_EOL . PHP_EOL;  //Test case separator

/**
/*
/* Test case end
/*
 */

//NULL, TRUE, FALSE 2 str func
function bool2str($v){if($v === NULL)return "NULL";elseif($v === FALSE)return "FALSE";elseif($v === TRUE)return "TRUE";else return "UNEXPECTED: '$v'";}

因此，我们可以看到并确认数组的比较运算符按预期和记录的方式工作！

<子> Full Testing File

对象比较运算符

<的文档  记录了here的>和/** /* /* Testing operators: < and > /* */ //Test case //Variations: amount, values and keys (order) //Test count: 10 // Failed: 0 // Passed: 10 { //Test case 1.1 $a = (object)["a" => 1]; $b = (object)["a" => 1]; //Passed var_dump("Same amount of elements, keys and values: " . "'<' -> " . bool2str($a < $b) . " '>' -> " . bool2str($a > $b)); //Test case 1.2 $a = (object)["a" => 1]; $b = (object)["a" => 1, "b" => 1]; //Passed var_dump("NOT same amount of elements, but same values: " . "'<' -> " . bool2str($a < $b) . " '>' -> " . bool2str($a > $b)); //Test case 1.3 $a = (object)["a" => 10]; $b = (object)["a" => 1, "b" => 1]; //Passed var_dump("NOT same amount of elements nor values: " . "'<' -> " . bool2str($a < $b) . " '>' -> " . bool2str($a > $b)); //Test case 1.4 $a = (object)["a" => 1]; $b = (object)["b" => 1]; //Passed var_dump("Same amount of element and values, NOT same keys: " . "'<' -> " . bool2str($a < $b) . " '>' -> " . bool2str($a > $b)); //Test case 1.5 $a = (object)["a" => 10]; $b = (object)["a" => 1]; //Passed var_dump("Same amount of elements and keys, NOT same values: " . "'<' -> " . bool2str($a < $b) . " '>' -> " . bool2str($a > $b)); //Test case 1.6 $a = (object)["a" => 1, "b" => 1]; $b = (object)["b" => 1, "a" => 1]; //Passed var_dump("Same amount of elements and keys in different order: " . "'<' -> " . bool2str($a < $b) . " '>' -> " . bool2str($a > $b)); //Test case 1.7 $a = (object)["a" => 1, "b" => 5]; $b = (object)["b" => 5]; //Passed var_dump("Same values, NOT same amount of elements nor keys: " . "'<' -> " . bool2str($a < $b) . " '>' -> " . bool2str($a > $b)); //Test case 1.8 $a = (object)["c" => 1]; $b = (object)["a" => 10]; //Passed var_dump("NOT same keys nor values: " . "'<' -> " . bool2str($a < $b) . " '>' -> " . bool2str($a > $b)); //Test case 1.9 $a = (object)["a" => 1, "b" => 1]; $b = (object)["b" => 10, "a" => 1]; //Passed var_dump("Same amount of elements and values, NOT same keys nor order: " . "'<' -> " . bool2str($a < $b) . " '>' -> " . bool2str($a > $b)); //Test case 1.10 class A {public $a = 1;} $a = new A; class B {public $a = 1;} $b = new B; //Passed var_dump("Same amount of elements and values and keys, but different not built-in class: " . "'<' -> " . bool2str($a < $b) . " '>' -> " . bool2str($a > $b)); } echo PHP_EOL . PHP_EOL . PHP_EOL; //Test case separator /** /* /* Test case end /* */ //NULL, TRUE, FALSE 2 str func function bool2str($v){if($v === NULL)return "NULL";elseif($v === FALSE)return "FALSE";elseif($v === TRUE)return "TRUE";else return "UNEXPECTED: '$v'";}：

┌───────────┬───────────┬──────────────────────────────────────────────────┐
│ type of   │ type of   │                                                  │
│ Operand 1 │ Operand 2 │ Result                                           │
├───────────┼───────────┼──────────────────────────────────────────────────┤
│ object    │ object    │ Built-in classes can define its own comparison,  │  
│           │           │ different classes are uncomparable,              │
│           │           │ same class compare properties same as arrays     │
└───────────┴───────────┴──────────────────────────────────────────────────┘

和以前一样，我们也可以测试一下：

==

包含对象的===和/** /* /* Testing operators: == and === /* */ //Test case //Variations: amount, values and keys (order) //Test count: 7 // Failed: 0 // Passed: 7 { //Test case 2.1 $a = (object)["a" => 1]; $b = (object)["a" => 1]; //Passed var_dump("Same amount of elements, values and keys: " . "'==' -> " . bool2str($a == $b) . " '===' -> " . bool2str($a === $b)); //Test case 2.2 $a = (object)["a" => 1]; $b = (object)["a" => 10, "b" => 1]; //Passed var_dump("NOT same amount of elements, but same values: " . "'==' -> " . bool2str($a == $b) . " '===' -> " . bool2str($a === $b)); //Test case 2.3 $a = (object)["a" => 10]; $b = (object)["a" => 1]; //Passed var_dump("Same amount of elements, but not values: " . "'==' -> " . bool2str($a == $b) . " '===' -> " . bool2str($a === $b)); //Test case 2.4 $a = (object)["a" => 1]; $b = (object)["b" => 1]; //Passed var_dump("Same amount of elements and values, but not keys: " . "'==' -> " . bool2str($a == $b) . " '===' -> " . bool2str($a === $b)); //Test case 2.5 $a = (object)["a" => 1, "b" => 2]; $b = (object)["b" => 2, "a" => 1]; //Passed var_dump("Same amount of elements, key and values, but different order: " . "'==' -> " . bool2str($a == $b) . " '===' -> " . bool2str($a === $b)); //Test case 2.6 class C {public $a = 1;} $a = new A; class D {public $a = 1;} $b = new B; //Passed var_dump("Same amount of elements and values and keys, but different not built-in class: " . "'==' -> " . bool2str($a == $b) . " '===' -> " . bool2str($a === $b)); //Test case 2.7 $a = (object)["a" => 1]; $b = $a; //Passed var_dump("Same exact instance: " . "'==' -> " . bool2str($a == $b) . " '===' -> " . bool2str($a === $b)); } echo PHP_EOL . PHP_EOL . PHP_EOL; //Test case separator /** /* /* Test case end /* */ //NULL, TRUE, FALSE 2 str func function bool2str($v){if($v === NULL)return "NULL";elseif($v === FALSE)return "FALSE";elseif($v === TRUE)return "TRUE";else return "UNEXPECTED: '$v'";}文档有自己的页面here：

  

使用比较运算符（==）时，会以简单的方式比较对象变量，即：如果两个对象实例具有相同的属性和值，则它们是相同的，并且是同一类的实例。

     

当使用标识运算符（===）时，当且仅当它们引用同一类的同一实例时，对象变量才相同。

再次对此进行测试：

<

所以我们看到，具有对象的比较运算符的行为与预期和记录完全一致！即使进行了宽松的比较，也要考虑属性和值。

<子> Full Testing File

结论

由于已报告此错误here，错误报告可能基于RFC中的评论，其中说明：

  

//仅比较值

但除此之外，这是RFC中唯一带有注释的示例，RFC明确指出它使用与==，>和if (!array_key_exists($key, $op2)) { return null; // uncomparable } 相同的比较规则。

这意味着提供的代码示例将无法比较，因为它没有相同的属性/键。

至于相等，它将需要相同的属性/键和值，因此它不能相等，并且比上面的代码示例中所示的无法比较的更少或更多：

$a = (object)["b" => "b"]; 
$b = (object)["a" => "b"]; 


var_dump($a > $b);   //FALSE
var_dump($a < $b);   //FALSE
var_dump($a == $b);  //FALSE

如果我们单独尝试每个比较运算符，我们也会看到这一点：

StdClass

所有返回false，因为它是无法比较的。

只是因为class A { public $a = ""; public $b = ""; } $a = new A; $a->a = "b"; unset($a->b); $b = new A; $b->b = "b"; unset($b->a); var_dump($a); var_dump($b); var_dump($a <=> $b); //1会有自己的比较，我们可以用我们自己的类测试它：

0

同样的输出：1。

所以我想说因为它无法比较，所以不应该返回1，-1或FALSE。它应该返回NULL或{{1}}或类似的东西。

现在我想说这种行为没有正确记录。

答案 1 :(得分：0)

echo $object1 <=> $object2; // 0

仅当

时才会返回0
  • $object1和$object2是同一类的实例
  • 和它们具有相同的属性和值。

在您的示例中，如果它返回0而不是1，我会感到惊讶。 也许是RFC中的拼写错误？

相关问题
最新问题