Shuffle new characters after each character in a string - php

Question

I have the following function to generate a new random character at the beginning and at the end of a string:
function random($string) {
$chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
$shuffle_start = substr(str_shuffle($chars), 0, 6);
$shuffle_end = substr(str_shuffle($chars), 0, 6);
$str = chunk_split($string, 1, substr(str_shuffle($chars), 0, 5));
return $shuffle_start . $str . $shuffle_end;
}
As you can see for $str I'm trying to get 5 random characters after each letter in the string and it's that I need some help with. As it is now, this function prints this:
dYj9quhDk2T4eDk2T4lDk2T4lDk2T4oDk2T4KHjN6T
The string is "hello" and are covered by 6 random characters at the beginning and at the end of the string (dYj9qu and KHjN6T). After each character inside of this string, you can see Dk2T4 and it's repeatably coming back after each character. This is not how I want it! I want Dk2T4 to be random so the string would look like this:
dYj9quhDk2T4eTft3bl7yjF4lac34vodkiY0KHjN6T
I want also the last characters of the string ("hello" - in this case dkiY0 in the last string) where removed from the string, so it looks like this:
dYj9quhDk2T4eTft3bl7yjF4lac34voKHjN6T
How can I fix this issue?

Answer 1

This happens because the chunk_split evaluates the substr(str_shuffle($chars), 0, 5) only once. You need to iterate the letters and generate the sequence for each one:
function random($string) {
$chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
$shuffle_start = substr(str_shuffle($chars), 0, 6);
$shuffle_end = substr(str_shuffle($chars), 0, 6);
$letters = str_split($string);
$str = '';
$count = count($letters);
foreach($letters as $l){
$count--;
$str .= $l;
if($count){ // add 5 characters if not last letter
$str .= substr(str_shuffle($chars), 0, 5);
}
}
return $shuffle_start . $str . $shuffle_end;
}