This page really ought to have table of assignment operators,
namely,

See the Arithmetic Operators page (
http://www.php.net/manual/en/language.operators.arithmetic.php )
Assignment    Same as:
$a += $b    $a = $a + $b    Addition
$a -= $b    $a = $a - $b    Subtraction
$a *= $b    $a = $a * $b    Multiplication
$a /= $b    $a = $a / $b    Division(
$a 除以 $b 的商,总是返回浮点数,即使两个运算数是整数(或由字符串转换成的整数)也是这样。注: 取模 $a % $b$a 为负值时的结果也是负值。)

$a %= $b    $a = $a % $b    Modulus(
$a 除以 $b 的余数

See the String Operators page(
http://www.php.net/manual/en/language.operators.string.php )
$a .= $b    $a = $a . $b      Concatenate(字符串连接,注意.=与+=区分)

See the Bitwise Operators page (
http://www.php.net/manual/en/language.operators.bitwise.php )
$a &= $b    $a = $a & $b    Bitwise And
$a |= $b    $a = $a | $b      Bitwise Or
$a ^= $b    $a = $a ^ $b      Bitwise Xor
$a <<= $b    $a = $a << $b    Left shift
$a >>= $b    $a = $a >> $b      Right shift