operator <=> 如何比较对象？
How operator <=> compare the objects?
在RFC给出这个例子：
// only values are compared
$a = (object) ["a" => "b"];
$b = (object) ["b" => "b"];
echo $a <=> $b; // 0
但是当我执行它时，我得到 1 作为输出：
$a = (object) ["a" => "b"];
$b = (object) ["b" => "b"];
echo $a <=> $b; //1
我现在不明白 <=> 是如何比较对象的？在 RFC 中它说它仅通过值进行比较。
P.S。我在 vagrant
下使用 PHP 7.0.4-6+deb.sury.org~trusty+1 (cli) ( NTS )
更新：
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
echo $object1 <=> $object2; // 0
这应该 return 0 仅当
$object1 和 $object2 是相同 class- 和它们具有相同的属性和值。
在你的例子中，如果它 return 0 而不是 1，我会感到惊讶。
可能是 RFC 中的拼写错误？
阅读RFC时发现自相矛盾：
Add a new operator (expr) <=> (expr), it returns 0 if both operands are equal, 1 if the left is greater, and -1 if the right is greater. It uses exactly the same comparison rules as used by our existing comparison operators: <, <=, ==, >= and >. (See the manual for details)
注：见==，意思是飞船算子比较松散
稍后在示例中：
// <b>only values are compared</b>
$a = (object) ["a" => "b"];
$b = (object) ["b" => "b"];
echo $a $b; // 0
宇宙飞船运算符只是运算符<、==和>的组合。它根据评估结果给出相应的 return 值：
operator(s): < = >
return value: -1 0 1
现在arrays and objects are a bit more complex types。要了解 <=> PHP 宇宙飞船运算符的作用，我们需要查看并了解 <、== 和 > 如何对数组和对象起作用。
那么让我们看看每种类型的比较运算符<、>、==。首先，我们将查看 < 和 >，然后再查看 ==.
数组比较运算符
现在关于数组 < 和 > 已记录 here:
┌───────────┬───────────┬──────────────────────────────────────────────────┐
│ type of │ type of │ │
│ Operand 1 │ Operand 2 │ Result │
├───────────┼───────────┼──────────────────────────────────────────────────┤
│ array │ array │ Array with fewer members is smaller, │
│ │ │ if key from operand 1 is not found in operand 2 │
│ │ │ then arrays are uncomparable, │
│ │ │ otherwise - compare value by value │
└───────────┴───────────┴──────────────────────────────────────────────────┘
这也可以写成code:
Example #2 Transcription of standard array comparison
<?php
// Arrays are compared like this with standard comparison operators
function standard_array_compare($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地对此进行测试。使用 methods like in math 并且总是只改变一件事，所以我们可以确保我们在这里是正确的：
/**
/*
/* 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 equality/identity 运算符 == 和 === 我们找到数组 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，我们可以简单地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！
对象比较运算符
< 的文档
并且 > 对象被记录在案 here:
┌───────────┬───────────┬──────────────────────────────────────────────────┐
│ 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这个：
/**
/*
/* 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'";}
== 和 === 对象的文档有自己的页面 here:
When using the comparison operator (==), object variables are compared in a simple manner, namely: Two object instances are equal if they have the same attributes and values, and are instances of the same class.
When using the identity operator (===), object variables are identical if and only if they refer to the same instance of the same class.
再次可以测试：
/**
/*
/* 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'";}
所以我们看到，对象的比较运算符的行为与预期和记录的完全一样！即使进行松散比较，也会考虑属性和值。
结论
由于已报告此错误 here，错误报告可能基于 RFC 中的评论，其中写道：
// only values are compared
但除了这是RFC中唯一一个有注释的例子外，RFC明确指出它使用与<、==和>相同的比较规则。
这意味着所提供的代码示例将无法比较，因为它没有相同的 attributes/keys。
至于相等性，它需要相同的 attributes/keys 和值，所以它不能相等，并且对于小于或大于它是不可比较的，如上面的代码示例所示，比较是如何工作的：
if (!array_key_exists($key, $op2)) {
return null; <b>// uncomparable</b>
}
如果我们单独尝试每个比较运算符，我们也会看到这一点：
$a = (object)["b" => "b"];
$b = (object)["a" => "b"];
var_dump($a > $b); //FALSE
var_dump($a < $b); //FALSE
var_dump($a == $b); //FALSE
全部 return 错误，因为它没有可比性。
而只是为了案例 StdClass 会有自己的比较，我们可以用我们自己的 class:
来测试它
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
同样的输出：1.
所以我想说，既然它是无可比拟的，它不应该 return 0、1 或 -1。它可能应该 return FALSE 或 NULL 或类似的东西。
现在我会说这种行为没有正确记录。
在RFC给出这个例子：
// only values are compared $a = (object) ["a" => "b"]; $b = (object) ["b" => "b"]; echo $a <=> $b; // 0
但是当我执行它时，我得到 1 作为输出：
$a = (object) ["a" => "b"];
$b = (object) ["b" => "b"];
echo $a <=> $b; //1
我现在不明白 <=> 是如何比较对象的？在 RFC 中它说它仅通过值进行比较。
P.S。我在 vagrant
下使用 PHP 7.0.4-6+deb.sury.org~trusty+1 (cli) ( NTS )更新：
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
echo $object1 <=> $object2; // 0
这应该 return 0 仅当
$object1和$object2是相同 class 的实例
- 和它们具有相同的属性和值。
在你的例子中，如果它 return 0 而不是 1，我会感到惊讶。
可能是 RFC 中的拼写错误？
阅读RFC时发现自相矛盾：
Add a new operator (expr) <=> (expr), it returns 0 if both operands are equal, 1 if the left is greater, and -1 if the right is greater. It uses exactly the same comparison rules as used by our existing comparison operators: <, <=, ==, >= and >. (See the manual for details)
注：见==，意思是飞船算子比较松散
稍后在示例中：
// <b>only values are compared</b> $a = (object) ["a" => "b"]; $b = (object) ["b" => "b"]; echo $a $b; // 0
宇宙飞船运算符只是运算符<、==和>的组合。它根据评估结果给出相应的 return 值：
operator(s): < = >
return value: -1 0 1
现在arrays and objects are a bit more complex types。要了解 <=> PHP 宇宙飞船运算符的作用，我们需要查看并了解 <、== 和 > 如何对数组和对象起作用。
那么让我们看看每种类型的比较运算符<、>、==。首先，我们将查看 < 和 >，然后再查看 ==.
数组比较运算符
现在关于数组 < 和 > 已记录 here:
┌───────────┬───────────┬──────────────────────────────────────────────────┐ │ type of │ type of │ │ │ Operand 1 │ Operand 2 │ Result │ ├───────────┼───────────┼──────────────────────────────────────────────────┤ │ array │ array │ Array with fewer members is smaller, │ │ │ │ if key from operand 1 is not found in operand 2 │ │ │ │ then arrays are uncomparable, │ │ │ │ otherwise - compare value by value │ └───────────┴───────────┴──────────────────────────────────────────────────┘
这也可以写成code:
Example #2 Transcription of standard array comparison
<?php // Arrays are compared like this with standard comparison operators function standard_array_compare($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地对此进行测试。使用 methods like in math 并且总是只改变一件事，所以我们可以确保我们在这里是正确的：
/**
/*
/* 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 equality/identity 运算符 == 和 === 我们找到数组 here:
┌───────────┬──────────┬──────────────────────────────────────────────────┐ │ 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，我们可以简单地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！
对象比较运算符
< 的文档
并且 > 对象被记录在案 here:
┌───────────┬───────────┬──────────────────────────────────────────────────┐ │ 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这个：
/**
/*
/* 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'";}
== 和 === 对象的文档有自己的页面 here:
When using the comparison operator (==), object variables are compared in a simple manner, namely: Two object instances are equal if they have the same attributes and values, and are instances of the same class.
When using the identity operator (===), object variables are identical if and only if they refer to the same instance of the same class.
再次可以测试：
/**
/*
/* 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'";}
所以我们看到，对象的比较运算符的行为与预期和记录的完全一样！即使进行松散比较，也会考虑属性和值。
结论
由于已报告此错误 here，错误报告可能基于 RFC 中的评论，其中写道：
// only values are compared
但除了这是RFC中唯一一个有注释的例子外，RFC明确指出它使用与<、==和>相同的比较规则。
这意味着所提供的代码示例将无法比较，因为它没有相同的 attributes/keys。
至于相等性，它需要相同的 attributes/keys 和值，所以它不能相等，并且对于小于或大于它是不可比较的，如上面的代码示例所示，比较是如何工作的：
if (!array_key_exists($key, $op2)) {
return null; <b>// uncomparable</b>
}
如果我们单独尝试每个比较运算符，我们也会看到这一点：
$a = (object)["b" => "b"];
$b = (object)["a" => "b"];
var_dump($a > $b); //FALSE
var_dump($a < $b); //FALSE
var_dump($a == $b); //FALSE
全部 return 错误，因为它没有可比性。
而只是为了案例 StdClass 会有自己的比较，我们可以用我们自己的 class:
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
同样的输出：1.
所以我想说，既然它是无可比拟的，它不应该 return 0、1 或 -1。它可能应该 return FALSE 或 NULL 或类似的东西。
现在我会说这种行为没有正确记录。