将字符串 PHP 中的每 3 个字符替换为“X”

Question

我需要每第三个字符用 X 替换每个字符

字符串 = "abcdefghijkl" 所需 output = "abxdexghxjkx"

我试过这个，但它取代了每一次出现

$str = "41610236ytm7eszf9d";

//to get the character every 3rd and save in $kept

$kept = preg_replace('/.{2}(.)/', "$1", $concatenated);
$find = str_split($kept);

$replace = array("X","X","X","X","X","X","X");

echo " <br> str_replace <br>"; 
 
echo str_replace($find, $replace, $str);
      echo "<br>";
     echo " <br> str_replace_first <br>"; 
 echo str_replace_first($kept, 'x', $concatenated); 
// outputs : 41X10X3XXtmXesXf9X

Answer 1

将 preg_replace 与此模式一起使用.{2}(.)并替换为$1只会保留替换后捕获组的值，并且不会添加 x 字符。

相反，您可以匹配(.{2}). 并替换为$1x

另一种选择是匹配 2 个字符，然后使用\K忘记匹配的内容，然后匹配单个字符，将替换为 x

$str = "41610236ytm7eszf9d";
echo  preg_replace('/..\K./', "x", $str);

Output

41x10x36xtmxesxf9x