如何高效替换字符串中的占位符变量？

优化“替换字符串中的占位符变量”

人们可能会遇到各种场景，其中识别和替换字符串中的占位符变量至关重要。此代码片段演示了一个动态替换函数 dynStr，它可以定位大括号 ({}) 括起来的键值对并相应地更新它们：

function dynStr($str,$vars) {
    preg_match_all("/\{[A-Z0-9_]+\}+/", $str, $matches);
    foreach($matches as $match_group) {
        foreach($match_group as $match) {
            $match = str_replace("}", "", $match);
            $match = str_replace("{", "", $match);
            $match = strtolower($match);
            $allowed = array_keys($vars);
            $match_up = strtoupper($match);
            $str = (in_array($match, $allowed)) ? str_replace("{".$match_up."}", $vars[$match], $str) : str_replace("{".$match_up."}", '', $str);
        }
    }
    return $str;
}

$variables = array("first_name" => "John","last_name" => "Smith","status" => "won");
$string = 'Dear {FIRST_NAME} {LAST_NAME}, we wanted to tell you that you {STATUS} the competition.';
echo dynStr($string,$variables); // Would output: 'Dear John Smith, we wanted to tell you that you won the competition.'

但是，正如作者强调的那样，此实现存在冗余数组访问并且显得计算密集。我们可以通过消除正则表达式的使用并根据“vars”数组中的键值对实现简单的字符串替换来简化这一过程：

$variables = array("first_name" => "John","last_name" => "Smith","status" => "won");
$string = 'Dear {FIRST_NAME} {LAST_NAME}, we wanted to tell you that you {STATUS} the competition.';

foreach($variables as $key => $value){
    $string = str_replace('{'.strtoupper($key).'}', $value, $string);
}

echo $string; // Dear John Smith, we wanted to tell you that you won the competition.

这种方法删除了不必要的嵌套数组遍历，并且简化替换过程，从而产生更干净、更高效的代码。

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