用PHP替换所有带有X或x的字母数字字符（区分大小写）

Question

I have the following variables:

$var1 = "23 Jan 2014";
$var2 = "Some Text Here - More Text is written here";

How can I replace the text so the output looks like this:

$var1 = "XX Xxx XXXX";
$var2 = "Xxxx Xxxx Xxxx - Xxxx Xxxx xx xxxxxx xxxx";

Edit: The variables can change. I simply want to replace all A-Za-z0-9 from any variable with X (for capital letters), x (for small letters) and X (for numbers).

Answer 1

Use double regular expressions - one for the upper case + numbers and one for the lower case. Something like this.

$var = preg_replace('/[A-Z0-9]/', 'X', $var);
$var = preg_replace('/[a-z]/', 'x', $var);