PHP Convert String to Hex and Hex to String

Encoding/decoding string in hexadecimal and back

Use pack() and unpack():

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

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

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

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

would produce

This is test => 546869732069732074657374 => This is test

PHP - Converting Hex string to uint64 and to int64

Finally managed to solve the problem

unpack("J",hex2bin("eb3dd796efda2409"));

seems hex2bin messed up the endianness so when we tried to do J it resolves correctly
Thank you for helping!

php string to hex with2's complement:

Solution you are looking for is as below,

It is referenced from one of the answer given at Create hex-representation of signed int in PHP.

<?php

function signed2hex($value, $reverseEndianness = true)
{
    $packed = pack('i', $value);
    $hex='';
    for ($i=0; $i < 4; $i++){
        $hex .= strtoupper( str_pad( dechex(ord($packed[$i])) , 2, '0', STR_PAD_LEFT) );
    }
    $tmp = str_split($hex, 2);
    $out = implode('', ($reverseEndianness ? array_reverse($tmp) : $tmp));
    return $out;
}

echo signed2hex(193390663);

C# conversion Hex to String does not match PHP Hex to String

I think your c# algorithm Hex2Str looks good, though I might suggest the following small change to avoid any possible inconsistencies with surrogate pair encoding:

    public static string Hex2Str(string hexString)
    {
        var sb = new StringBuilder();

        var len = hexString.Length / 2;
        for (var i = 0; i < len; i++)
        {
            // Convert the number expressed in base-16 to an integer. 
            int value = Convert.ToInt32(hexString.Substring(i * 2, 2), 16);
            string stringValue = Char.ConvertFromUtf32(value);
            sb.Append(stringValue);
        }

        return sb.ToString();
    }

The real problem here, I suspect, is that the string from PHP is being mangled when passed through the console due to inconsistent encodings. For instance, if the PHP console has Latin 9 (ISO) encoding and your input console has OEM United States encoding (which it is on my computer) then 'à' will be transformed to 'α'.

Instead, I recommend taking the additional step of encoding your PHP string in Base64 using base64_encode before writing it to the console. This will guarantee a pure ASCII representation as it is passed through the console. Then decode as follows:

    public static string FromPHPBase64String(string phpString)
    {
        var bytes = Convert.FromBase64String(phpString);
        var sb = new StringBuilder();
        foreach (var b in bytes)
        {
            string stringValue = char.ConvertFromUtf32(b);
            sb.Append(stringValue);
        }
        return sb.ToString();
    }

I believe everything should now match.

PHP convert string to \xnn hex

Should work

function strhex($string) {
  $hexstr = unpack('H*', $string);
  return array_shift($hexstr);
}

Update

Code below what you need

function strtohex($string)
{
  $string = str_split($string);
  foreach($string as &$char)
    $char = "\x".dechex(ord($char));
  return implode('',$string);
}

print strtohex("[0-9A-Za-z\+/=]*");