<?php
echo "\n0:\$a = $a \$b = $b\n";
$a = ($b = 4) + 5; // $a is equal to 9 now, and $b has been set to 4.
echo "\n1:\$a = $a \$b = $b\n";
?>

<?php
echo "\n0:\$a = $a \$b = $b\n";
$a = 3;
echo "\n1:\$a = $a \$b = $b\n";
$a += 5; // sets $a to 8, as if we had said: $a = $a + 5;
echo "\n2:\$a = $a \$b = $b\n";
$b = "Hello ";
echo "\n3:\$a = $a \$b = $b\n";
$b .= "There!"; // sets $b to "Hello There!", just like $b = $b . "There!";
echo "\n4:\$a = $a \$b = $b\n";
?>

ARRAY OPERATORS:

<?php
$a = array("a" => "apple", "b" => "banana");
$b = array("a" => "pear", "b" => "strawberry", "c" => "cherry");
var_dump($a);
var_dump($b);

$c = $a + $b; // Union of $a and $b
echo "Union of \$a and \$b: \n";
var_dump($c);

$c = $b + $a; // Union of $b and $a
echo "Union of \$b and \$a: \n";
var_dump($c);

$a += $b; // Union of $a += $b is $a and $b
echo "Union of \$a += \$b: \n";
var_dump($a);
?>