您需要在preg_replace参数中对它们进行双重转义"(一次用于字符串，一次用于regex引擎):

You need to "double escape" them inside preg_replace parameters (once for the string, once for the regex engine):

$mystring = 'c:\windows\system32\drivers\etc\hosts';
$escaped = preg_replace('/\\\\/','\\\\\\\\',$mystring);

echo "New string is:  $escaped\n";

或如果使用str_replace仅一次:

 $newstring = str_replace('\\','\\\\',$mystring);

 echo "str_replace : $newstring\n";
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