如何在IF语句中用value运算符语句实现变量？

Question

如何在IF语句中用值运算符语句实现变量？

    if ($dcustomer['mix_max']=='MIN') {
            $operator=">=";
         } elseif ($dcustomer['mix_max']=='MAX') {
            $operator="<=";
        }


        if ($djml['Tamount'] ."$operator". $dcustomer['limit_maksimal']){
}

Answer 1

你不能（好吧，如果你使用了eval()就可以了，出于显而易见的原因应该避免使用它。）

但乘数可以达到同样的效果：

switch ($dcustomer['mix_max']) {
    case 'MIN':
        $multiplier = 1;
        break;
    case 'MAX':
        $multiplier = -1;
        break;
    default:
        // Always prepare for the unknown :-)
        throw new \Exception("Unknown operator");
 }
 if ($djml['Tamount']*$multiplier >= $dcustomer['limit_maksimal']*$multiplier) {
     ...
 }

但我认为它会更清晰，更灵活：

$condition = null;
switch ($dcustomer['mix_max']) {
    case 'MIN':
        $condition = ($djml['Tamount'] >= $dcustomer['limit_maksimal']);
        break;
    case 'MAX':
        $condition = ($djml['Tamount'] <= $dcustomer['limit_maksimal']);
        break;
    default:
        // Always prepare for the unknown :-)
        throw new \Exception("Unknown operator");
 }
 if ($condition) {
     ...
 }

Answer 2

<?php

$dcustomer = array("mix_max"=>"MIN","limit_maksimal"=>2);
$djml = array("Tamount"=>"");

if ($dcustomer['mix_max']=='MIN') {
    $operator=">=";
} elseif ($dcustomer['mix_max']=='MAX') {
    $operator="<=";
}


echo $djml['Tamount'] .$operator. $dcustomer['limit_maksimal'];