$a=5;
$b=&$a;
$a=8;
echo $b;
// prints  8
$a=5;
$b=$a;  //no &
$a=8;
echo $b;
// prints 5

php >     $a=5;
php >     $b=&$a;
php >     $a=8;
php >     echo $b;
8
php >     // prints  8
php >     $a=5;
php >     $b=$a;  //no &
php >     $a=8;
php >     echo $b;
8
php >     // prints 5

php > $b=3;
php > echo $a;
3

php >    $e=5; $f=$e; $e=6; echo $f;
5

$a = 5;    // creates a "slot", puts 5 in it, makes $a point to it
$b =& $a;  // makes $b point to the same "slot" $a points to
$c = 6;    // creates a "slot", puts 6 in it, makes $c point to it
$a = $c;   // puts the value of the slot $c points to into the slot $a points to
echo $b;   // outputs the value of the slot $b points to (6)

$b = $a

$value = 5;
$alias = &$value;
$value = 8;
echo $alias;   # 8
$value = 5;
$alias = $value; # no &
$value = 8;
echo $alias;   # 8 (OP expected 5)

$alias = $value; # no &

$value = $value;

$alias = &$other;

unset($alias);