<?php
 /* PHP不使用速算扣除数计算个人所得税
 * @author 吴先成
 * @param float $salary 含税收入金额
 * @param float $deduction 保险等应当扣除的金额 默认值为0
 * @param float $threshold 起征金额 默认值为3500
 * @return float | false 返回值为应缴税金额 参数错误时返回false
 */
 function getPersonalIncomeTax($salary, $deduction=0, $threshold=3500){
 if(!is_numeric($salary) || !is_numeric($deduction) || !is_numeric($threshold)){
  return false;
 }
 if($salary <= $threshold){
  return 0;
 }
 $levels = array(1500, 4500, 9000, 35000, 55000, 80000, PHP_INT_MAX);
 $rates = array(0.03, 0.1, 0.2, 0.25, 0.3, 0.35, 0.45);
 $taxableIncome = $salary - $threshold - $deduction;
 $tax = 0;
 foreach($levels as $k => $level){
  $previousLevel = isSet($levels[$k-1]) ? $levels[$k-1] : 0;
  if($taxableIncome <= $level){
  $tax += ($taxableIncome - $previousLevel) * $rates[$k];
  break;
  }
  $tax += ($level-$previousLevel) * $rates[$k];
 }
 $tax = round($tax, 2);
 return $tax;
 }
 /* 示例 */
 echo getPersonalIncomeTax(10086.11);
 //运行结果：762.22
?>