How to convert string back and forth to binary - php

Question

I need to be able to turn a string into its binary parts. Say I have the string:
"R!Testing"
I want a function to return the respective binary:
"010100100010000101010100011001010111001101110100011010010110111001100111"
and also have another function to also turn that binary in the string "R!Testing" for example. Currently I am using the following.
function messageToBinary($message) {
$value = unpack('H*', $message);
return base_convert($value[1], 16, 2);
}
// Turn string of bits into its text equivalent
function binaryToMessage($binary) {
return pack('H*', base_convert($binary, 2, 16));
}
This of course has several issues I believe. Some characters fail (I think because 16 is the max?) to convert properly and also base_convert sometimes fails with large strings due to overflow issues.
What is a better approach?

Answer 1

Do it in a loop instead of trying to treat the whole thing as one big number. ord() returns the character code of a character, and sprintf() can be used to convert that to a fixed-length binary number.
function messageToBinary($message) {
$len = strlen($message);
$result = '';
for ($i = 0; $i < $len; $i++) {
$result .= sprintf("%08b", ord($message[$i]));
}
return $result;
}
To go the other way, extract 8-bit segments of the string, convert them from binary to decimal, then use chr() to convert that to a character.
function binaryToMessage($binary) {
$len = strlen($binary);
$result = '';
for ($i = 0; $i < $len; $i += 8) {
$n = substr($binary, $i, 8);
$result .= chr(bindec($n));
}
return $result;
}
Note that this only works for 8-bit characters. For Unicode, you'll need to get more complex.