(PHP 4, PHP 5)
bcsub — Subtract one arbitrary precision number from another
$left_operand
   , string $right_operand
   [, int $scale
  ] )
   Subtracts the right_operand from the
   left_operand.
  
left_operand
     The left operand, as a string.
right_operand
     The right operand, as a string.
scale此可选参数用于设置结果中小数点后的小数位数。 也可通过使用 bcscale() 来设置全局默认的小数位数,用于所有函数。
The result of the subtraction, as a string.
Example #1 bcsub() example
<?php
$a = '1.234';
$b = '5';
echo bcsub($a, $b);     // -3
echo bcsub($a, $b, 4);  // -3.7660
?>