Php language.oop.object comparison () function

Write your php code

Comparing objects

In PHP 4, objects are compared in a very simple manner, namely: Two object instances are equal if they have the same attributes and values, and are instances of the same class. Similar rules are applied when comparing two objects using the identity operator (===).

If we were to execute the code in the example below:

Example 18-1. Example of object comparison in PHP 4


<?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 {
    var $flag;

    function Flag($flag=true) {
            $this->flag = $flag;
    }
}

class SwitchableFlag extends Flag {

    function turnOn() {
        $this->flag = true;
    }

    function turnOff() {
        $this->flag = false;
    }
}

$o = new Flag();
$p = new Flag(false);
$q = new Flag();

$r = new SwitchableFlag();

echo "Compare instances created with the same parameters\n";
compareObjects($o, $q);

echo "\nCompare instances created with different parameters\n";
compareObjects($o, $p);

echo "\nCompare an instance of a parent class with one from a subclass\n";
compareObjects($o, $r);
?>

The above example will output:

Compare instances created with the same parameters
o1 == o2 : TRUE
o1 != o2 : FALSE
o1 === o2 : TRUE
o1 !== o2 : FALSE

Compare instances created with different parameters
o1 == o2 : FALSE
o1 != o2 : TRUE
o1 === o2 : FALSE
o1 !== o2 : TRUE

Compare an instance of a parent class with one from a subclass
o1 == o2 : FALSE
o1 != o2 : TRUE
o1 === o2 : FALSE
o1 !== o2 : TRUE

Which is the output we will expect to obtain given the comparison rules above. Only instances with the same values for their attributes and from the same class are considered equal and identical.

Even in the cases where we have object composition, the same comparison rules apply. In the example below we create a container class that stores an associative array of Flag objects.

Example 18-2. Compound object comparisons in PHP 4


<?php
class FlagSet {
    var $set;

    function FlagSet($flagArr = array()) {
        $this->set = $flagArr;
    }

    function addFlag($name, $flag) {
        $this->set[$name] = $flag;
    }

    function removeFlag($name) {
        if (array_key_exists($name, $this->set)) {
            unset($this->set[$name]);
        }
    }
}


$u = new FlagSet();
$u->addFlag('flag1', $o);
$u->addFlag('flag2', $p);
$v = new FlagSet(array('flag1'=>$q, 'flag2'=>$p));
$w = new FlagSet(array('flag1'=>$q));

echo "\nComposite objects u(o,p) and v(q,p)\n";
compareObjects($u, $v);

echo "\nu(o,p) and w(q)\n";
compareObjects($u, $w);
?>

The above example will output:

Composite objects u(o,p) and v(q,p)
o1 == o2 : TRUE
o1 != o2 : FALSE
o1 === o2 : TRUE
o1 !== o2 : FALSE

u(o,p) and w(q)
o1 == o2 : FALSE
o1 != o2 : TRUE
o1 === o2 : FALSE
o1 !== o2 : TRUE

Php language.oop.object comparison Function syntax tag

language.oop.object comparison php code on this is provided for your study purpose, it will guide you to know how create and design a website using php. use it to practice and train your self online

Php language.oop.object comparison syntax tutorial

php tutorial guide and code design are for easy learning and programming. The code practice section provided at the top is for practising of this syntax. Use the code section up to practice your php programming online. Learning php is very easy, all you need is to use the examples on this site and practice them to perfect your skills.