PHP References

What is reference

A reference is a method to accesses same variable contents with other names or just like other variable.

It’s functionality looks like pointer but It’s not like C(C programming language) pointer. C language performs this type functionality via pointer and C pointer uses actual memory address to denote reference.

PHP variables and it’s content are different to each other. So there are any same content have different names {$variable}.

 

References syntax

There are reference uses & symbol to perform it’s own operations of references.

<?php

$x =& $y;

?>

 

Output:

 

What references do

PHP references performs three basic operations, These are given here:

• Assign By Reference

• Pass By Reference

• Return By Reference

 

Assign By Reference

In this two variables named $x and $y have been refers to same content is [CONTENT].

There are $x and $y are completely equal to each other in variable’s value.

It does not points to each other, but These both variables points to content [CONTENT] or same place.

 

 

Understand references with an example:

<?php

function foo(&$var) { }

foo($a); // $a is "created" and assigned to null

$b = array();
foo($b['b']);
var_dump(array_key_exists('b', $b)); // bool(true)

$c = new StdClass;
foo($c->d);
var_dump(property_exists($c, 'd')); // bool(true)

?>

 

Pass By Reference

The second thing references do is to pass variables by reference.

This is done by making a local variable in a function and a variable in the calling scope referencing the same content.

Example:

<?php

function foo(&$var)
{
    $var++;
}

$a=5;
foo($a);

?>

 

Return By Reference

Returning by reference is useful when you want to use a function to find to which variable a reference should be bound.

Do not use return-by-reference to increase performance. The engine will automatically optimize this on its own.

Example:

<?php
class foo {
    public $value = 42;

    public function &getValue() {
        return $this->value;
    }
}

$obj = new foo;
$myValue = &$obj->getValue(); // $myValue is a reference to $obj->value, which is 42.
$obj->value = 2;
echo $myValue;                // prints the new value of $obj->value, i.e. 2.

?>

 

Note:

 

Note:

 

How to unset a reference

<?php

$x = 1;
$y =& $x;
unset($x);

?>

 

won't unset $y, just $x.