替换字符串中的占位符变量

Question

刚刚完成这个功能。基本上，它假设查看一个字符串并尝试找到任何占位符变量，这些变量将放置在两个大括号{} 之间。它获取大括号之间的值，并使用它来查看应该匹配键的数组。然后它将字符串中的大括号变量替换为匹配键的数组中的值。

但它有一些问题。首先是当我var_dump($matches) 时，它会将结果放入一个数组中，在一个数组内。所以我必须使用两个foreach() 才能获得正确的数据。

我也觉得它很重，我一直在检查它，试图让它变得更好，但我有点难过。我错过了哪些优化？

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.'

Answer 1

我认为对于这样一个简单的任务你不需要使用 RegEx：

$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.

Answer 2

我希望我加入派对还不算太晚——我会这样做：

function template_substitution($template, $data)
{
    $placeholders = array_map(function ($placeholder) {
        return strtoupper("{{$placeholder}}");
    }, array_keys($data));

    return strtr($template, array_combine($placeholders, $data));
}

$variables = array(
    'first_name' => 'John',
    'last_name' => 'Smith',
    'status' => 'won',
);

$string = 'Dear {FIRST_NAME} {LAST_NAME}, we wanted to tell you that you have {STATUS} the competition.';

echo template_substitution($string, $variables);

而且，如果您有任何机会可以使您的 $variables 键与您的占位符完全匹配，那么解决方案将变得非常简单：

$variables = array(
    '{FIRST_NAME}' => 'John',
    '{LAST_NAME}' => 'Smith',
    '{STATUS}' => 'won',
);

$string = 'Dear {FIRST_NAME} {LAST_NAME}, we wanted to tell you that you have {STATUS} the competition.';

echo strtr($string, $variables);

（参见 PHP 手册中的strtr()。）

考虑到 PHP 语言的性质，我相信这种方法应该会在该线程中列出的所有方法中产生最佳性能。

---

编辑： 7 年后重新审视这个答案后，我注意到我身边有一个潜在的危险疏忽，这也是 pointed out by another user。一定要以支持的形式拍拍他们的后背！

如果您对编辑前的答案感兴趣，请查看the revision history

Answer 3

我认为您可以通过以下方式大大简化您的代码（除非我误解了某些要求）：

$allowed = array("first_name"=>"John","last_name"=>"Smith","status"=>"won");

$resultString = preg_replace_callback(

    // the pattern, no need to escape curly brackets
    // uses a group (the parentheses) that will be captured in $matches[ 1 ]
    '/{([A-Z0-9_]+)}/',

    // the callback, uses $allowed array of possible variables
    function( $matches ) use ( $allowed )
    {
        $key = strtolower( $matches[ 1 ] );
        // return the complete match (captures in $matches[ 0 ]) if no allowed value is found
        return array_key_exists( $key, $allowed ) ? $allowed[ $key ] : $matches[ 0 ];
    },

    // the input string
    $yourString
);

PS.：如果要从输入字符串中删除不允许的占位符，请替换

return array_key_exists( $key, $allowed ) ? $allowed[ $key ] : $matches[ 0 ];

与

return array_key_exists( $key, $allowed ) ? $allowed[ $key ] : '';

Answer 4

提醒未来登陆此页面的人：使用foreach 循环和/或str_replace 方法的所有答案（包括已接受的答案）都容易被替换为good ol' Johnny { STATUS} 的名称带有Johnny won。

Decent Dabbler 的 preg_replace_callback 方法和 U-D13 的第二个选项（但不是第一个）是我看到目前发布的唯一不受此影响的选项，但由于我没有足够的声誉来添加评论我想我会写一个完全不同的答案。

如果您的替换值包含用户输入，更安全的解决方案是使用 strtr 函数而不是 str_replace 以避免重新替换可能出现在您的值中的任何占位符。

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

// bonus one-liner for transforming the placeholders
// but it's ugly enough I broke it up into multiple lines anyway :)
$replacement = array_combine(
    array_map(function($k) { return '{'.strtoupper($k).'}'; }, array_keys($variables)),
    array_values($variables)
);

echo strtr($string, $replacement);

输出：Dear John {STATUS}, we wanted to tell you that you won the competition. 而 str_replace 输出：Dear John won, we wanted to tell you that you won the competition.

Answer 5

这是我使用的函数：

function searchAndReplace($search, $replace){
    preg_match_all("/\{(.+?)\}/", $search, $matches);

    if (isset($matches[1]) && count($matches[1]) > 0){
        foreach ($matches[1] as $key => $value) {
            if (array_key_exists($value, $replace)){
                $search = preg_replace("/\{$value\}/", $replace[$value], $search);
            }
        }
    }
    return $search;
}


$array = array(
'FIRST_NAME' => 'John',
'LAST_NAME' => 'Smith',
'STATUS' => 'won'
);

$paragraph = 'Dear {FIRST_NAME} {LAST_NAME}, we wanted to tell you that you {STATUS} the competition.';

// outputs: Dear John Smith, we wanted to tell you that you won the competition.

只需将一些文本传递给它以进行搜索，以及一个包含替换的数组。

Answer 6

/**
   replace placeholders with object
**/
$user = new stdClass();
$user->first_name = 'Nick';
$user->last_name = 'Trom';

$message = 'This is a {{first_name}} of a user. The user\'s {{first_name}} is replaced as well as the user\'s {{last_name}}.';

preg_match_all('/{{([0-9A-Za-z_]+)}}/', $message, $matches);

foreach($matches[1] as $match)
{
    if(isset($user->$match))
        $rep = $user->$match;
    else
        $rep = '';

    $message = str_replace('{{'.$match.'}}', $rep, $message);
}

echo $message;