<?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
?>