不能在php中显示运算符

Question

我正在尝试做一个数字游戏，其中生成两个数字，并且每次键入答案时都会相加或相减。我可以让数字显示，但我不能让操作员显示。我会怎么做？这里是我的代码：

PHP

<?php 

$num1 = rand(0, 20); 
$num2 = rand(0, 20); 

$operators = array(
    "+", 
    "-", 
); 

switch ($operators[array_rand($operators)]) { 
    case "+": 
     $result = $num1 + $num2; 
     break; 
    case "-": 
     $result = $num1 - $num2; 
     break; 
} 
    echo' 
     <div class="row">     
      <div class="col-md-3 col-md-offset-1">'. $num1 .'</div> 
      <div class="col-md-3 col-md-offset-1">'. $operators .'</div> 
      <div class="col-md-3 col-md-offset-1">'. $num2 .'</div> 

     </div>   
     ' 
?> 

Answer 1

<?php 

$num1 = rand(0, 20); 
$num2 = rand(0, 20); 

$operators = array(
    "+", 
    "-", 
); 
$operator = $operators[array_rand($operators)]; 
switch ($operator) { 
    case "+": 
     $result = $num1 + $num2; 
     break; 
    case "-": 
     $result = $num1 - $num2; 
     break; 
} 
    echo' 
     <div class="row">     
      <div class="col-md-3 col-md-offset-1">'. $num1 .'</div> 
      <div class="col-md-3 col-md-offset-1">'. $operator .'</div> 
      <div class="col-md-3 col-md-offset-1">'. $num2 .'</div> 

     </div>   
     ' 
?> 

Answer 2

尝试somethinf像这样...

<?php 

$num1 = rand(0, 20); 
$num2 = rand(0, 20); 

$operators = array("+","-", 
); 
$operator = $operators[array_rand($operators)]; 
switch ($operator) { 
    case "+": 
     $result = $num1 + $num2; 
     break; 
    case "-": 
     $result = $num1 - $num2; 
     break; 
} 
    echo' 
     <div class="row"> 
      <div class="col-md-3 col-md-offset-1">'. $num1 .'</div> 
      <div class="col-md-3 col-md-offset-1">'. $operator.'</div> 
      <div class="col-md-3 col-md-offset-1">'. $num2 .'</div> 

     </div> 
     ' 
?> 

Answer 3

<?php 

$num1 = rand(0, 20); 
$num2 = rand(0, 20); 

$operators = array(
    "+", 
    "-", 
); 



switch ($operator=$operators[array_rand($operators)]) { 
    case "+": 
     $result = $num1 + $num2; 
     break; 
    case "-": 
     $result = $num1 - $num2; 
     break; 
} 
    echo' 
     <div class="row">     
      <div class="col-md-3 col-md-offset-1">'. $num1 .'</div> 
      <div class="col-md-3 col-md-offset-1">'. $operator .'</div> 
      <div class="col-md-3 col-md-offset-1">'. $num2 .'</div> 


     </div>   
     ' 
?>