PHP - Create a valid byte string

Question

INTRO

I have two strings of bytes. The first one is created starting from an array of hex codes and using a for cicle to create the byte string:

$codes = ["02", "66", "6c", "6a", "3a", "03"];
$bytestring1 = "";
for ($i = 0; $i < count($codes); $i++) $byteString1 .= "\x" . $codes[$i];

The second string is created writing it directly by hand:

$bytestring2 = "\x02\x66\x6c\x6a\x3a\x03";

WHAT I EXPECT

I expect that $bytestring1 and $bytestring2 are identical.

WHAT HAPPENS

When I send $bytestring1 and $bytestring2 to a client using socket_send command, the variable $bytestring1 appears to be a pure string and it doesn't work.

The variable $bytestring2, instead, is recognized as a string of bytes and it works.

QUESTION

How can I create a valid string of bytes using the first method?

Thanx.

stackoverflow.com/questions/885597/string-to-byte-array-in-php — Death-is-the-real-truth
– Death-is-the-real-truth, Commented Mar 20, 2018 at 11:18
"\x02" is a PHP string literal notation which expresses the byte 02. "\x" doesn't mean anything in particular, and concatenating it with "02" just results in the string "\x02"; strings' values aren't recursively interpreted at any time to resolve possible meanings that mean something in string literal notation. I.e. it would be pretty surprising behaviour if $userinput1 . $userinput2 would be interpreted and result in the byte 02 because it happens to form the value "\x02". — deceze
– deceze ♦, Commented Mar 20, 2018 at 11:24
I don't understand the reason of this unuseful and long reply, when vuryss user has replied in a very useful way. Sorry, but your reply doesn't help anyone. — Stevenworks Pictures
– Stevenworks Pictures, Commented Mar 21, 2018 at 11:07

vuryss · Accepted Answer · 2018-03-20 11:20:22Z

4

Use http://php.net/manual/en/function.hex2bin.php

Like that:

$codes = ["02", "66", "6c", "6a", "3a", "03"];
$byteString1 = hex2bin(implode('', $codes));

answered Mar 20, 2018 at 11:20

vuryss

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