Php 用一个字符串替换多个字符串

我试图用PHP中的一个字符串替换几个可能的字符串。此外，字符串必须只匹配一个完整的单词：

<?

$rawstring = "Hello NONE. Your N/A is a pleasure to have! Your friend Johanna is also here.";

//strings for substitution
$placeholders = array('N/A', 'NA', 'NONE');

//replace with blank spaces. 
$substitution = array('');

$greeting = str_ireplace($placeholders, $substitution, $rawstring);

echo  $greeting . "<br />";
?>

这几乎就是我想要的输出。 我希望替换只影响单个单词。在本例中，它将替换“Johanna”中的“na”，从而生成“Johan”。它仍然应该打印出“Johanna”

这可能吗

---

编辑：我无法控制$rawstring。这只是一个例子。

我设置了一个关联数组来设置替换变量。 -编辑，必须在N/A中转义斜杠

$val_to_swap_in = '';
$replacers = array(
    '/NONE/' => $val_to_swap_in,
    '/N\/A/' => $val_to_swap_in, 
    '/NA/'   => $val_to_swap_in,
);
$greeting = preg_replace(array_keys($replacers), array_values($replacers),  $rawstring);

在php cli shell中导致此问题：

Hello . Your  is a pleasure to have! Your friend Johanna is also here.

---

我想看看你是否已经知道了弦，并且只是想在某些点上下潜。很抱歉，我没有足够的代表发表评论。

若要与单词的某些部分不匹配，您需要使用

preg\u replace（）

试着这样做：

$rawstring = "Hello NONE. Your N/A is a pleasure to have! Your friend Johanna is also here.";
$placeholders = array('N/A', 'NA', 'NONE');

//Turn $placeholders into an array of regular expressions
//  `#` delimits the regular expression. Make sure this doesn't appear in $placeholders.
//  `(.+)` matches and captures any string of characters
//  `\b` matches word boundaries
//  `${1}` reinserts the captured pattern.
//  `i` at the end makes this case insensitive.
$re = preg_replace('#(.+)#', '#\b${1}\b#i', $placeholders); 

//Make the same substitution for all matches.
$substitution = '';

$greeting = preg_replace($re, $substitution, $rawstring);
echo  $greeting;

---

不幸的是，我无法控制传入的字符串。我无法替换令牌。将替换为字符串（

$substitution=''；

）将为您进行替换。更棘手的部分只是替换“整词”。为此，常用的方法是使用a和，如

$result=preg_replace（'/\bSQUIRREL\b/i'，kitty'，噢，看，一只松鼠！'）$rawstring = "Hello NONE. Your N/A is a pleasure to have! Your friend Johanna is also here.";
$placeholders = array('N/A', 'NA', 'NONE');

//Turn $placeholders into an array of regular expressions
//  `#` delimits the regular expression. Make sure this doesn't appear in $placeholders.
//  `(.+)` matches and captures any string of characters
//  `\b` matches word boundaries
//  `${1}` reinserts the captured pattern.
//  `i` at the end makes this case insensitive.
$re = preg_replace('#(.+)#', '#\b${1}\b#i', $placeholders); 

//Make the same substitution for all matches.
$substitution = '';

$greeting = preg_replace($re, $substitution, $rawstring);
echo  $greeting;