Question

我如何做到这一点?

$v1=105;
$v2=90;
if ($value== subtraction ){
    $operator= - ;
}else{
    $operator= + ;
}

$new_value=$v1.$operator.$v2;

因此,它应当归还105-90=15或105+90=195。但是,我怎样才能将发行人变数作为经营人? 例如,这项工作:

eval("$new_value=$v1".$operator."$v2");

得到帮助!

Answer 1

我建议而不是这样做,但为了使用<代码>eval,你必须这样做:

// You need to escape the $ in $new_value
eval("$new_value = $v1 $operator $v2");

我建议这样做,而是这样(即:对经营者来说,不要使用一个变量,就像计算那样):

$v1=105;
$v2=90;
if ($value== subtraction ){
    $new_value= $v1 - $v2;
}else{
    $new_value= $v1 + $v2;
}

Answer 2

The other answer is better, but if you really want to do something tricky, I think you can have a variable hold a function (instead of an operator).

//untested hypothetical example

$myOperation = function Add($num1, $num2){
  return $num1+$num2;
}

在公共卫生和社会福利部中,没有这样做,但我想到的是can。

Answer 3

<?php
$v1 = 105;
$v2 = 90;
if($value== subtraction )
    $v2 *= -1;
$new_value = $v1 + $v2;
?>

Answer 4

为什么不使美元使用人发挥作用?

$v1 = 10;
$v2 = 20;

$substraction = function($a, $b) {
    return $a - $b;
};

[...]

$someString =  substraction ;
echo $$someString($v1,$v2);