References inside the constructor
To prove what is written above let us watch
the code below.
<?php
// now we will change the name. what do you expect?
// you could expect that both $bar1 and $globalref[0] change
their names...
$bar1->setName('set from outside');
// as mentioned before this is not the case.
$bar1->echoName();
$globalref[0]->echoName();
/* output:
set from outside
set in constructor */
// let us see what is different with $bar2 and $globalref[1]
$bar2->setName('set from outside');
// luckily they are not only equal, they are the same variable
// thus $bar2->name and $globalref[1]->name are the
same too
$bar2->echoName();
$globalref[1]->echoName();
/* output:
set from outside
set from outside */
?>
Another final example, try to understand it.
<?php
class A {
function A($i) {
$this->value = $i;
// try to figure out why we do not need a reference here
$this->b = new B($this);
}
function createRef() {
$this->c = new B($this);
}
function echoValue() {
echo "<br />","class ",get_class($this),':
',$this->value;
}
}
class B {
function B(&$a) {
$this->a = &$a;
}
function echoValue() {
echo "<br />","class ",get_class($this),':
',$this->a->value;
}
}
// try to understand why using a simple copy here would
yield
// in an undesired result in the *-marked line
$a =& new A(10);
$a->createRef();
$a->echoValue();
$a->b->echoValue();
$a->c->echoValue();
$a->value = 11;
$a->echoValue();
$a->b->echoValue(); // *
$a->c->echoValue();
?>
This example will output:
class A: 10
class B: 10
class B: 10
class A: 11
class B: 11
class B: 11
