PHPの変数代入の原理を深く理解する

$a = 1;

$b = '2';

$c = [4, 5, 6];

$d = new stdClass();

$a1 = $a;

$b1 = $b;

$c1 = $c;

$d1 = $d;

// Common assignment

$v = '1';

$c = $v;

$c = '2';

echo $v, PHP_EOL; // '1'

// Arrays are also normal assignments

$arr1 = [1,2,3];

$arr2 = $arr1;

$arr2[1] = 5;

print_r($arr1); // [1, 2, 3]

// Objects are assigned by reference

class A {

    public $name = 'I am A';

}

$a = new A();

$b = $a;

echo $a->name, PHP_EOL; // 'I am A'

echo $b->name, PHP_EOL; // 'I am A'

$b->name = 'I am B';

echo $a->name, PHP_EOL; // 'I am B'

// Use cloning to solve the reference passing problem

class Child{

    public $name = 'I am A1's subordinate';

}

class A1 {

    public $name = 'I am A';

    public $child;

    function __construct(){

        $this->child = new Child();

    }

    function __clone(){

        $this->name = $this->name;

        // new or use Child's clone either

        // $this->child = new Child();

        $this->child = clone $this->child;

    }

}

a1 = new A1();

echo $a1->name, PHP_EOL; // output the original content of a1

echo $a1->child->name, PHP_EOL;

$b1 = $a1;

echo $b1->name, PHP_EOL; // b1 is now also the content of a1

echo $b1->child->name, PHP_EOL;

$b1->name = 'I am B1'; // b1 modifies the content

$b1->child->name = 'I am B1's subordinate';

echo $a1->name, PHP_EOL; // a1 becomes the content of b1

echo $a1->child->name, PHP_EOL;

// Use __clone

$b2 = clone $b1; // b2 clones b1

$b2->name = 'I am B2'; // b2 modifies the content

$b2->child->name = 'I am B2's subordinate';

echo $b1->name, PHP_EOL; // b1 doesn't become what b2 modifies

echo $b1->child->name, PHP_EOL;

echo $b2->name, PHP_EOL; // b2 modified content is fine, b1, b2 is not a cargo anymore

echo $b2->child->name, PHP_EOL;

// Assigning by reference

$b = &$v;

$b = '3';

echo $v, PHP_EOL;