Split string into 3 random-length parts - php

Question

I have a string and I want to split it into 3 random-length parts (without caring about string length is the objective) to get 3 strings.
$mystring = "aHR0cHM6Ly93d3cucGhwLm5ldC9tYW51YWwvZW4vZnVuY3Rpb24uc3RyLXNwbGl0LnBocA==";
When I tried to use str_split(), I always have to manually set the number of character per string.
If I calculate the string length and divide it by 3, sometimes I get non-whole numbers.
$len = strlen($mystring);
$len = $len / 3;
$parts = str_split($mystring, $len);
print_r($parts);

Answer 1

Even if you want random then I assume you still don't want 0 length strings.
I use random values between 1 and string length (minus some, to make sure you don't run out of characters).
$mystring = "aHR0cHM6Ly93d3cucGhwLm5ldC9tYW51YWwvZW4vZnVuY3Rpb24uc3RyLXNwbGl0LnBocA==";
$len=strlen($mystring);
$parts[] = substr($mystring, 0, $l[] = rand(1,$len-5));
$parts[] = substr($mystring, $l[0], $l[] = rand(1,$len-$l[0]-3));
$parts[] = substr($mystring, array_sum($l));
print_r($parts);
The code grabs parts of the string depending on what the previous random value was.
https://3v4l.org/v4nUF

Answer 2

A more generic solution could look like this:
function split_random_parts($string, $part_count) {
$result = [];
for ($i = 0; $i < $part_count - 1; $i++) {
// Always leave part_count - i characters remaining so that no empty string gets created
$len = rand(1, strlen($string) - ($part_count - $i));
$result[] = substr($string, 0, $len);
$string = substr($string, $len);
}
$result[] = $string;
return $result;
}

Answer 3

Something like this would do it:
$mystring = "aHR0cHM6Ly93d3cucGhwLm5ldC9tYW51YWwvZW4vZnVuY3Rpb24uc3RyLXNwbGl0LnBocA==";
$part3 = substr($mystring, rand(2,(strlen($mystring)-2)));
$mystring = substr($mystring, 0, (strlen($mystring)-strlen($part3)));
$part2 = substr($mystring, rand(1,(strlen($mystring)-1)));
$mystring = substr($mystring, 0, (strlen($mystring)-strlen($part2)));
$part1 = $mystring;
var_dump($part1, $part2, $part3);
This code would produce results such as:
string(67) "aHR0cHM6Ly93d3cucGhwLm5ldC9tYW51YWwvZW4vZnVuY3Rpb24uc3RyLXNwbGl0LnB"
string(1) "o"
string(4) "cA=="
string(57) "aHR0cHM6Ly93d3cucGhwLm5ldC9tYW51YWwvZW4vZnVuY3Rpb24uc3RyL"
string(5) "XNwbG"
string(10) "l0LnBocA=="
string(31) "aHR0cHM6Ly93d3cucGhwLm5ldC9tYW5"
string(27) "1YWwvZW4vZnVuY3Rpb24uc3RyLX"
string(14) "NwbGl0LnBocA=="
string(5) "aHR0c"
string(23) "HM6Ly93d3cucGhwLm5ldC9t"
string(44) "YW51YWwvZW4vZnVuY3Rpb24uc3RyLXNwbGl0LnBocA=="

Answer 4

I mean you just need to round up the result of length division like:
<?php
$mystring = "The any size string ...";
$len=strlen($mystring);
$chunk=ceil($len/3);
$parts = str_split($mystring , $chunk);
print_r($parts);
Here the fiddle

Answer 5

If you need divide to 3 without random length, may you use str_pad like
$str = 'aHR0cHM6Ly93d3cnVuY3Rpb24uc3RyLXNwbGl0LnBocA==';
$divide = 3;
$char = '*'; // that not used in your string
$add = $divide - strlen($str) % $divide;
$total = strlen($str) + $add;
$str = str_pad($str, $total, $char, STR_PAD_LEFT);
//string(48) "**aHR0cHM6Ly93d3cnVuY3Rpb24uc3RyLXNwbGl0LnBocA=="
$result = str_split($str, $total / $divide );
/*array(3) {
[0]=> string(16) "**aHR0cHM6Ly93d3"
[1]=> string(16) "cnVuY3Rpb24uc3Ry"
[2]=> string(16) "LXNwbGl0LnBocA=="
}*/
keep in mind that strip '*' chars before decode
$result = str_replace('*', '', $result);
Demo

Answer 6

Because your input string contains no whitespace characters, you can use sscanf() with %s placeholders with explicit substring lengths (for the first two substrings) to explode the string on dynamic points.
Code: (Demo)
$mystring = "aHR0cHM6Ly93d3cucGhwLm5ldC9tYW51YWwvZW4vZnVuY3Rpb24uc3RyLXNwbGl0LnBocA==";
$len = strlen($mystring);
$end_of_first = rand(1, $len - 2);
$end_of_middle = rand(1, $len - $end_of_first - 1);
var_export(sscanf($mystring, "%{$end_of_first}s%{$end_of_middle}s%s"));
For anyone else who might have whitespaces in their input string, you can replace the s with [^~] where the ~ should be a character that is guaranteed to not occur in your string.
For an approach that accommodates a variable number of segments, a decementing loop seems appropriate.
Code: (Demo)
$totalSegments = 4;
$segments = [];
while ($totalSegments) {
--$totalSegments;
$segmentLength = rand(1, strlen($mystring) - $totalSegments);
[$segments[], $mystring] = sscanf($mystring, "%{$segmentLength}s%s");
}
var_export($segments);