反转正则表达式,从正则表达式创建字符串

$regex = '#^en/cities/([^/]+?)/$#';
$replace = array('paris');

$result = preg_replace_callback('#^^|([^)]*)|$$#',function($m)use($replace){
    static $index = 0;
    if($m[0] === '^' || $m[0] === '$'){return '';}
    if(isset($replace[$index])){
        return $replace[$index++];
    }
    return $m[0];
},substr($regex,1,-1));
echo $result; // en/cities/paris/

Online demo

我已经使它“灵活”,所以你可以添加更多的值！

$regex = '#^en/cities/([^/]+?)/region/([^/]+?)$#'; // <<< changed
$replace = array('paris','nord'); // <<< changed

$result = preg_replace_callback('#^^|([^)]*)|$$#',-1));
echo $result; // en/cities/paris/region/nord

Online demo

说明：

$regex = '#^en/cities/([^/]+?)/region/([^/]+?)$#'; // Regex to "reverse"
$replace = array('paris','nord'); // Values to "inject"

/*  Regex explanation:
   #   Start delimiter
       ^^         Match "^" at the begin (we want to get ride of this)
       |           Or
       ([^)]*)   Match "(",anything zero or more times until ")" is found,")"
       |           Or
       $$        Match "$" at the end (we want to get ride of this)
   #   End delimiter
*/

$result = preg_replace_callback('#^^|([^)]*)|$$#',function($m)use($replace){
    static $index = 0; // Set index 0,note that this variable is only accessible in this (anonymous) function
    if($m[0] === '^' || $m[0] === '$'){return '';} // Get ride of ^/$at the begin and the end
    if(isset($replace[$index])){ // Always check if it exists,for example if there were not enough values in $replace,this will prevent an error ...
        return $replace[$index++]; // Return the injected value,at the same time increment $index by 1
    }
    return $m[0]; // In case there isn't enough values,this will return ([^/]+?) in this case,you may want to remove it to not include it in the output
},-1)); // substr($regex,-1) => Get ride of the delimiters
echo $result; // output o_o

_{Note: This works only on PHP 5.3+}