note 123692 added to language.references.whatare

The following three code snippets show the effect of using references in scalar variables, arrays and objects under different circumstances. In any case the result is the expected one if you stick to the concept that a reference is an alias to a variable. After assigning by reference ( no matter if $a =& $b or $b =& $a ) both variable names refer to the same variable. References with scalars <?php /* References are aliases for the same variable */ $a = 1; $b =& $a; $b = 2; echo "$a,$b\n"; // 2,2 $a = 3; echo "$a,$b\n"; // 3,3 // Variables can be bound before being assigned $c =& $d; $c = 4; echo "$c,$d\n"; // 4,4 ?> References with arrays <?php /* Array elements referencing scalar variables */ $a = 1; $b = 2; $c = array(&$a, &$b); $a = 3; $b = 4; echo "c: $c[0],$c[1]\n"; // 3,4 $c[0] = 5; $c[1] = 6; echo "a,b: $a,$b\n"; // 5,6 /* Reference between arrays */ $d = array(1,2); $e =& $d; $d[0] = 3; $d[1] = 4; echo "e: $e[0],$e[1]\n"; // 3,4 $e[0] = 5; $e[1] = 6; echo "d: $d[0],$d[1]\n"; // 5,6 $e = 7; echo "d: $d\n"; // 7 ( $d is no more an array, but an integer ) /* Iterating an array of references using foreach construct */ $a = 1; $b = 2; $f = array(&$a,&$b); foreach($f as $x) // If $x is assigned by value it doesn't change referred variables. $x = 3; echo "a,b: $a,$b\n"; // 1,2 foreach($f as &$x) // If $x is assigned by reference it changes referred variables. $x = 3; echo "a,b: $a,$b\n"; // 3,3 // Be aware that, after the loop, $x still references $f[1] and so $b $x = 4; echo "a,b: $a,$b\n"; // 3,4 ( $b affected ) // To avoid previous side effects it is advisable to unset x, unlinking it from $f[1] and $b unset($x); $x = 5; echo "a,b: $a,$b\n"; // 3,4 ( $b not affected ) ?> References with objects <?php /* Object property referencing a scalar variable */ $a = 1; $b = new stdClass(); $b->x =& $a; $a = 2; echo "b->x: $b->x\n"; // 2 $b->x = 3; echo "a: $a\n"; // 3 /* Reference between objects */ $c = new stdClass(); $c->x = 1; $d =& $c; $d->x = 2; echo "c->x: $c->x\n"; // 2 $d = new stdClass(); $d->y = 3; echo "c->y: $c->y\n"; // 3 echo "c->x: $c->x\n"; // Undefined property: stdClass::$x ?> ---- Server IP: 208.43.231.9 Probable Submitter: 82.199.157.34 (proxied: 181.47.208.104) ---- Manual Page -- http://php.net/manual/en/language.references.whatare.php Edit -- https://master.php.net/note/edit/123692 Del: integrated -- https://master.php.net/note/delete/123692/integrated Del: useless -- https://master.php.net/note/delete/123692/useless Del: bad code -- https://master.php.net/note/delete/123692/bad+code Del: spam -- https://master.php.net/note/delete/123692/spam Del: non-english -- https://master.php.net/note/delete/123692/non-english Del: in docs -- https://master.php.net/note/delete/123692/in+docs Del: other reasons-- https://master.php.net/note/delete/123692 Reject -- https://master.php.net/note/reject/123692 Search -- https://master.php.net/manage/user-notes.php