Encoding/decoding string in hexadecimal and back

Question

Given a string that may contain any character (including a unicode characters), how can I convert this string into hexadecimal representation, and then reverse and obtain from hexadecimal this string?

You should choose an accepted answer. The poster gets reputation credit for it. — fool4jesus
– fool4jesus, Commented Jan 19, 2015 at 14:14

Marcin Orlowski · Accepted Answer · 2023-09-06 18:34:40Z

18

Use pack() and unpack():

function hex2str($hex) {
  return pack('H*', $hex);
}

function str2hex($str) {
  $unpacked = unpack('H*', $str);
  return array_shift($unpacked);
}

$txt = 'This is test';
$hex = str2hex($txt);
$str = hex2str($hex);

echo "{$txt} => {$hex} => {$str}\n";

would produce

This is test => 546869732069732074657374 => This is test

edited Sep 6, 2023 at 18:34

answered Nov 24, 2012 at 13:51

Marcin Orlowski

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3 Comments

bluantinoo Over a year ago

This is awesome, why unpack() works, while dechex() not? and furthermore, unpack is not just for binary strings?

Potherca Over a year ago

This will trigger a notice: PHP Notice: Only variables should be passed by reference

Marcin Orlowski Over a year ago

Ah, it was about directly passing result of unpack() to array_shift(). Fixed, thanks.

Praveen Kumar Purushothaman · Accepted Answer · 2012-11-24 13:53:54Z

Use a function like this:

<?php
function bin2hex($str) {
    $hex = "";
    $i = 0;
    do {
        $hex .= dechex(ord($str{$i}));
        $i++;
    } while ($i < strlen($str));
    return $hex;
}

// Look what happens when ord($str{$i}) is 0...15
// you get a single digit hexadecimal value 0...F

// bin2hex($str) could return something like 4a3,
// decimals(74, 3), whatever the binary value is of those.

function hex2bin($str) {
    $bin = "";
    $i = 0;
    do {
        $bin .= chr(hexdec($str{$i}.$str{($i + 1)}));
        $i += 2;
    } while ($i < strlen($str));
    return $bin;
}

// hex2bin("4a3") just broke. Now what?

// Using sprintf() to get it right.
function bin2hex($str) {
    $hex = "";
    $i = 0;
    do {
        $hex .= sprintf("%02x", ord($str{$i}));
        $i++;
    } while ($i < strlen($str));
    return $hex;
}

// now using whatever the binary value of decimals(74, 3)
// and this bin2hex() you get a hexadecimal value you can
// then run the hex2bin function on. 4a03 instead of 4a3.
?>

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Encoding/decoding string in hexadecimal and back

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Use a function like this:

Source: http://php.net/manual/en/function.bin2hex.php

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Use a function like this:

Source: http://php.net/manual/en/function.bin2hex.php

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