A simple example of PHP judging whether the brackets in the expression match

The following editor will bring you a simple example of PHP judging whether the brackets in the expression match. The editor thinks it’s pretty good, so I’ll share it with you now and give it as a reference. Let’s follow the editor and take a look.

is as follows:

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<?php  
/** 
 * title: 判断表达式中括号是否匹配 
 * Description: () 匹配 )(不匹配 利用压栈和出栈 
 * @author Mr Lv   

 */   
function isValid($expstr) { 
  $temp = array(); 
  for ($i=0; $i<strlen($expstr); $i++) { 
    $ch = $expstr[$i]; 
    switch($ch) { 
      case &#39;(&#39;: 
        array_push($temp, &#39;(&#39;); 
        break; 
      case &#39;)&#39;: 
        if (empty($temp) || array_pop($temp) != &#39;(&#39;) { 
          return "缺少左括号（"; 
        } 
    } 
  } 
  return empty($temp) == true ? "表达式匹配" : "缺少右括号）"; 
} 
$expstrA = "(1+3(6*4)-(2+3))()("; 
$expstrB = "(1+3(6*4)-(2+3))()"; 
$expstrC = "(1+3(6*4)-(2+3)))"; 
echo isValid($expstrA); 
echo "<br>"; 
echo isValid($expstrB); 
echo "<br>"; 
echo isValid($expstrC); 
?>

Page information:

缺少右括号） 
表达式匹配 
缺少左括号（

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