Mẹo về Hướng dẫn compare object php 2022 Chi Tiết

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Thủ Thuật về Hướng dẫn compare object php Chi Tiết

Bạn đang tìm kiếm từ khóa Hướng dẫn compare object php được Update vào lúc : 2022-09-13 21:00:31 . Với phương châm chia sẻ Thủ Thuật Hướng dẫn trong nội dung nội dung bài viết một cách Chi Tiết 2022. Nếu sau khi Read nội dung nội dung bài viết vẫn ko hiểu thì hoàn toàn hoàn toàn có thể lại Comment ở cuối bài để Admin lý giải và hướng dẫn lại nha.

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 (values are compared with ==), 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.

An example will

clarify these rules.

Example #1 Example of object comparison

<?php
function bool2str($bool)

    if ($bool === false) 
        return ‘FALSE’;
     else 
        return ‘TRUE’;
    

function

compareObjects(&$o1, &$o2)

    echo ‘o1 == o2 : ‘ . bool2str($o1 == $o2) . “n”;
    echo ‘o1 != o2 : ‘ . bool2str($o1 != $o2) . “n”;
    echo ‘o1 === o2 : ‘ . bool2str($o1 === $o2) . “n”;
    echo ‘o1 !== o2 : ‘ . bool2str($o1 !== $o2) . “n”;

class

Flag

    public $flag;

    function

__construct($flag = true) 
        $this->flag = $flag;
    

class

OtherFlag

    public $flag;

    function

__construct($flag = true) 
        $this->flag = $flag;
    
$o = new Flag();
$p.. = new Flag();
$q = $o;
$r = new OtherFlag();

echo

“Two instances of the same classn”;
compareObjects($o, $p..);

echo

“nTwo references to the same instancen”;
compareObjects($o, $q);

echo

“nInstances of two different classesn”;
compareObjects($o, $r);
?>

The above example will output:

Two instances of the same class

o1 == o2 : TRUE

o1 != o2 : FALSE

o1 === o2 : FALSE

o1 !== o2 : TRUE

Two references to the same instance

o1 == o2 : TRUE

o1 != o2 : FALSE

o1 === o2 : TRUE

o1 !== o2 : FALSE

Instances of two different classes

o1 == o2 : FALSE

o1 != o2 : TRUE

o1 === o2 : FALSE

o1 !== o2 : TRUE

Note:

Extensions can define own rules for their objects comparison (==).

jazfresh

hotmail ¶

15 years ago

Note that when comparing object attributes, the comparison is recursive ( least, it is with PHP 5.2). That is, if $a->x contains an object then that will be compared with $b->x in the same manner. Be aware that this can lead to recursion errors:
<?php
class Foo
    public $x;

$a = new Foo();
$b = new Foo();
$a->x = $b;
$b->x = $a;print_r($a == $b);
?>
Results in:
PHP Fatal error:  Nesting level too deep – recursive dependency? in test.php on line 11

Anonymous

12

years ago

Comparison using operators should be documented.  Between two objects, least in PHP5.3, the comparison operation stops and returns the first unequal property found.

<?php

$o1

= new stdClass();
$o1->prop1 = ‘c’;
$o1->prop2 = 25;
$o1->prop3 = 201;
$o1->prop4 = 1000;$o2 = new stdClass();
$o2->prop1 = ‘c’;
$o2->prop2 = 25;
$o2->prop3 = 200;
$o2->prop4 = 9999;

echo (int)(

$o1 < $o2); // 0
echo (int)($o1 > $o2); // 1$o1->prop3 = 200;

echo (int)(

$o1 < $o2); // 1
echo (int)($o1 > $o2); // 0?>

rnealxp yahoo dot com

2 years ago

Please use this corrected version of function “valuesAreIdentical” instead of that which I previously posted (dependencies found in previous post); if an Admin can just replace the fn snippet, awesome/thanks, otherwise, apologies.
<?php
    public static function valuesAreIdentical($v1, $v2):bool
        $type1 = gettype($v1);
        $type2 = gettype($v2);
        switch(true)
            case ($type1 !== $type2):
                return false;
            case ($type1===’boolean’ //end switch
   
?>

rnealxp yahoo dot com

5 years ago

These three functions call themselves recursively and handle any nesting levels of arrays/objects/values and do strict comparisons. The entry-point to this function set would be “valuesAreIdentical”.

<?php
function valuesAreIdentical($v1, $v2): bool
    $type1 = gettype($v1);
    $type2 = gettype($v2);

    if(

$type1 !== $type2)
        return false;
   

    switch(

true) $type1===’integer’ //end switch

    //All tests passed.

return true;

function

objectsAreIdentical($o1, $o2): bool
    //See if loose comparison passes.
    if($o1 != $o2)
        return false;
    //Now do strict(er) comparison.
    $objReflection1 = new ReflectionObject($o1);
    $objReflection2 = new ReflectionObject($o2);$arrProperties1 = $objReflection1->getProperties(ReflectionProperty::IS_PUBLIC);
    $arrProperties2 = $objReflection2->getProperties(ReflectionProperty::IS_PUBLIC);$bool = arraysAreIdentical($arrProperties1, $arrProperties2);
    if($bool===false)
        return false;
   

    foreach(

$arrProperties1 as $key=>$propName)
        $bool = valuesAreIdentical($o1->$propName, $o2->$propName);
        if($bool===false)
            return false;
       
    //All tests passed.
    return true;

function

arraysAreIdentical(array $arr1, array $arr2): bool
    $count = count($arr1);//Require that they have the same size.
    if(count($arr2) !== $count)
        return false;
    //Require that they have the same keys.
    $arrKeysInCommon = array_intersect_key($arr1, $arr2);
    if(count($arrKeysInCommon)!== $count)
        return false;
    //Require that their keys be in the same order.
    $arrKeys1 = array_keys($arr1);
    $arrKeys2 = array_keys($arr2);
    foreach($arrKeys1 as $key=>$val)
        if($arrKeys1[$key] !== $arrKeys2[$key])
            return false;
       
    //They do have same keys and in same order.
    foreach($arr1 as $key=>$val)
        $bool = valuesAreIdentical($arr1[$key], $arr2[$key]);
        if($bool===false)
            return false;
       
    //All tests passed.
    return true;

?>

nhuhoai

8 years ago

For comparison about two objects in a class, you can use an interface like this and customize your functions for each class:

<?php
interface EQU
    public static function compare( EQU $me, EQU $you );
    public function equals( EQU $you );

?>

If you gotcha a super class, you can make generic functions (not safe but work with not complex class):

<?php
abstract class SuperClass
    public function __construct( )
        // do what you need
   
    public static function compare( $obj1, $obj2 )
        return serialize( $obj1 ) == serialize( $obj2 );
   
    public function equals( $obj )
        return static::compare( $this, $obj );
   

?>

wbcarts juno dot com

14 years ago

COMPARING OBJECTS using PHP’s usort() method.

PHP and MySQL both provide ways to sort your data already, and it is a good idea to use that if possible. However, since this section is on comparing your own PHP objects (and that you may need to alter the sorting method in PHP), here is an example of how you can do that using PHP’s “user-defined” sort method, usort() and your own class compare() methods.

<?php/*
* Employee.php
*
* This class defines a compare() method, which tells PHP the sorting rules
* for this object – which is to sort by emp_id.
*
*/
class Employee

    public $first;
    public $last;
    public $emp_id;     // the property we’re interested in…public function __construct($emp_first, $emp_last, $emp_ID)
   
        $this->first = $emp_first;
        $this->last = $emp_last;
        $this->emp_id = $emp_ID;
    /*
     * define the rules for sorting this object – using emp_id.
     * Make sure this function returns a -1, 0, or 1.
     */
    public static function compare($a, $b)
   
        if ($a->emp_id emp_id) return -1;
        else if($a->emp_id == $b->emp_id) return 0;
        else return 1;
   

    public function

__toString()
   
        return “Employee[first=$this->first, last=$this->last, emp_id=$this->emp_id]”;
   
# create a PHP array and initialize it with Employee objects.
$employees = array(
  new Employee(“John”, “Smith”, 345),
  new Employee(“Jane”, “Doe”, 231),
  new Employee(“Mike”, “Barnes”, 522),
  new Employee(“Vicky”, “Jones”, 107),
  new Employee(“John”, “Doe”, 2),
  new Employee(“Kevin”, “Patterson”, 89)
);# sort the $employees array using Employee compare() method.
usort($employees, array(“Employee”, “compare”));# print the results
foreach($employees as $employee)

  echo $employee . ‘
’;

?>

Results are now sorted by emp_id:

Employee[first=John, last=Doe, emp_id=2]
Employee[first=Kevin, last=Patterson, emp_id=89]
Employee[first=Vicky, last=Jones, emp_id=107]
Employee[first=Jane, last=Doe, emp_id=231]
Employee[first=John, last=Smith, emp_id=345]
Employee[first=Mike, last=Barnes, emp_id=522]

Important Note: Your PHP code will never directly call the Employee’s compare() method, but PHP’s usort() calls it many many times. Also, when defining the rules for sorting, make sure to get to a “primitive type” level… that is, down to a number or string, and that the function returns a -1, 0, or 1, for reliable and consistent results.

Also see: ://.php/manual/en/function.usort.php for more examples of PHP’s sorting facilities.

rune zedeler dot dk

15 years ago

Whoops, apparently I hadn’t checked the array-part of the below very well.
Forgot to test if the arrays had same length, and had some misaligned parenthesis.
This one should work better :+)

<?
function deepCompare($a,$b)
  if(is_object($a) && is_object($b))
    if(get_class($a)!=get_class($b))
      return false;
    foreach($a as $key => $val)
      if(!deepCompare($val,$b->$key))
        return false;
   
    return true;
 
  else if(is_array($a) && is_array($b))
    while(!is_null(key($a)) && !is_null(key($b)))
      if (key($a)!==key($b)
    return is_null(key($a)) && is_null(key($b));
 
  else
    return $a===$b;

?>

cross+php distal dot com

14 years ago

In response to “rune zedeler dot dk”s comment about class contents being equal, I have a similar issue.  I want to sort an array of objects using sort().

I know I can do it with usort(), but I’m used to C++ where you can define operators that allow comparison.  I see in the zend source code that it calls a compare_objects function, but I don’t see any way to implement that function for an object.  Would it have to be an extension to provide that interface?

If so, I’d like to suggest that you allow equivalence and/or comparison operations to be defined in a class definition in PHP.  Then, the sorts of things rune and I want to do would be much easier.

rune zedeler dot

dk ¶

15 years ago

I haven’t found a build-in function to check whether two obects are identical – that is, all their fields are identical.
In other words,

<?
class A
  var $x;
  function __construct($x) $this->x = $x;

$identical1 = new A(42);
$identical2 = new A(42);
$different = new A(’42’);
?>

Comparing the objects with “==” will claim that all three of them are equal. Comparing with “===” will claim that all are un-equal.
I have found no build-in function to check that the two identicals are
identical, but not identical to the different.

The following function does that:

<?
function deepCompare($a,$b)
  if(is_object($a) && is_object($b))
    if(get_class($a)!=get_class($b))
      return false;
    foreach($a as $key => $val)
      if(!deepCompare($val,$b->$key))
    return false;
   
    return true;
 
  else if(is_array($a) && is_array($b))
    while(!is_null(key($a) && !is_null(key($b)))) !deepCompare(current($a),current($b)))
    return false;
      next($a); next($b);
   
    return true;
 
  else
    return $a===$b;

?>

Hayley Watson

13 years

ago

This has already been mentioned (see jazfresh hotmail’s note), but here it is again in more detail because for objects the difference between == and === is significant.

Loose equality (==) over objects is recursive: if the properties of the two objects being compared are themselves objects, then those properties will also be compared using ==.

<?php
class Link

    public $link; function __construct($link) $this->link = $link;

class Leaf

    public $leaf; function __construct($leaf) $this->leaf = $leaf;
$leaf1 = new Leaf(42);
$leaf2 = new Leaf(42);$link1 = new Link($leaf1);
$link2 = new Link($leaf2);

echo

“Comparing Leaf object equivalence: is $leaf1==$leaf2? “, ($leaf1 == $leaf2  ? “Yes” : “No”), “n”;
echo “Comparing Leaf object identity: is $leaf1===$leaf2? “,   ($leaf1 === $leaf2 ? “Yes” : “No”), “n”;
echo “n”;
echo “Comparing Link object equivalence: is $link1==$link2? “,($link1 == $link2  ? “Yes” : “No”), “n”;
echo “Comparing Link object identity: is $link1===$link2? “,  ($link1 === $link2 ? “Yes” : “No”), “n”;
?>

Even though $link1 and $link2 contain different Leaf objects, they are still equivalent because the Leaf objects are themselves equivalent.

The practical upshot is that using “==” when “===” would be more appropriate can result in a severe performance penalty, especially if the objects are large and/or complex. In fact, if there are any circular relationships involved between the objects or (recursively) any of their properties, then a fatal error can result because of the implied infinite loop.

<?php
class Foo public $foo;
$t = new Foo; $t->foo = $t;
$g = new Foo; $g->foo = $g;

echo

“Strict identity:   “, ($t===$g ? “True” : “False”),”n”;
echo “Loose equivalence: “, ($t==$g  ? “True” : “False”), “n”;
?>

So preference should be given to comparing objects with “===” rather than “==”; if two distinct objects are to be compared for equivalence, try to do so by examining suitable individual properties. (Maybe PHP could get a magic “__equals” method that gets used to evaluate “==”? 🙂 )

Oddant

9 years ago

This example is way too much confusing, if you new to php comparison motor, you should think (after reading this example) that ‘==’ is actually comparing the type of the objects. that’s not true, it actually compares the type of the objects AND the properties of them.

<?php

class A

    private $value;

    function __construct ($value)

   

        $this->value = $value;

   

class B

    private $value;

    function __construct ($value)

   

        $this->value = $value;

   

$a1 = new A (1);

$a2 = new A (2);

$b1 = new B (1);

var_dump( $a1 == $a2 );

var_dump( $a1 == $b1 );

?>

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