unpacking a binary number (string)

[CyberLawrence]

This might be an easy fix.

I need to break an 8 bit binary number into 8 separate variables. When using unpack(), it pushes the first zeros it finds to the back as NULLs

0111 1111 gets translated at 1111 111 null

$binary3 = 01111111;

list($b7, $b6, $b5, $b4, $b3, $b2, $b1, $b0) = array_values(unpack('c*', $binary3));

var_dump($b7, $b6, $b5, $b4, $b3, $b2, $b1, $b0);

 

My OUTPUT

-----HIBYTE------
7f HEX
01111111
-----LOBYTE------
7f HEX
01111111
-----DATABYTE------
7f HEX
01111111
---------------

int(49) int(49) int(49) int(49) int(49) int(49) int(49) NULL
int(49) int(49) int(49) int(49) int(49) int(49) int(49) NULL
int(49) int(49) int(49) int(49) int(49) int(49) int(49) NULL

Bit 0 is
Bit 1 is 49
Bit 2 is 49
Bit 3 is 49
Bit 4 is 49
Bit 5 is 49
Bit 6 is 49
Bit 7 is 49

 

[requinix]

1 hour ago, CyberLawrence said:

I need to break an 8 bit binary number into 8 separate variables.

Let's forget unpack() for a minute.

Is the variable a number or a string? Because what you have in this code

$binary3 = 01111111;

is not a binary number.

[Barand]

Still forgetting unpack(), for 8 bits to 8 vars

$binary3 = 0b10110001;

for ($k=0; $k<8; $k++) {
    $vars[$k]  = ($binary3 & 2**$k) ? 1:0;
}

giving

$vars = Array
            (
                [0] => 1
                [1] => 0
                [2] => 0
                [3] => 0
                [4] => 1
                [5] => 1
                [6] => 0
                [7] => 1
            )

 

[CyberLawrence]

13 hours ago, Barand said:

Still forgetting unpack(), for 8 bits to 8 vars

$binary3 = 0b10110001;

for ($k=0; $k<8; $k++) {
    $vars[$k]  = ($binary3 & 2**$k) ? 1:0;
}

giving

$vars = Array
            (
                [0] => 1
                [1] => 0
                [2] => 0
                [3] => 0
                [4] => 1
                [5] => 1
                [6] => 0
                [7] => 1
            )

 

I'll give Barand's solution a try.

I am taking in HEX from a html form (FF, EF, A1....) then using baseconvert to convert that to binary. that's where the "binary" is coming from.

Obviously its not true binary...

After the HEX gets converted... shouldn't it look like this as Barand has it? 0b10110001

[requinix]

43 minutes ago, CyberLawrence said:

After the HEX gets converted... shouldn't it look like this as Barand has it? 0b10110001

Not quite. It will look like

var_dump(base_convert("A1", 16, 2));

whatever that says it looks like.

[CyberLawrence]

15 minutes ago, requinix said:

Not quite. It will look like

var_dump(base_convert("A1", 16, 2));

whatever that says it looks like.

string(8) "10100001"

[requinix]

There ya go: it's not a number but a string containing some number of digits - perhaps less than 8 of them if the number was <=127.

So what's your next thought?

[CyberLawrence]

Apparently I'm not getting what I need from the form, ie. actual numbers. I must be getting strings of numbers without base types? 0b, 0x, ..

I gotta look over some HTML code... or find out how to convert the string into a number.

[ginerjm]

form vars from html are always received as strings in php.

[requinix]

PHP will get exactly what you typed into the form. Typed 1010101? That's what you'll get. Typed 85? That's what you'll get.

Decide whether you want the input to be the completely obscure binary representation of a number or to be the very familiar human concept of a decimal number (cough) then validate the input accordingly: binary would be up to 8 digits of 0 and 1, a number would be something 0-255.

What you do next depends on whether it was the binary or decimal digits, but either way you've got lots of options available: bitwise math, base_convert, str_split, string offsets, substr... The list goes on, so decide what kind of process would make sense to you and find the PHP code to express it.

[CyberLawrence]

Entering as HEX via the HTML form... converting to binary in order to get individual bits as variables. My breakdown is between the form and assigning the binary representation to a variable name.

Barand's code is fine...  I just need to get to this point ---> $binary3 = 0b10110001;

from this point

$WORD =   $_POST["BYTE"];

$binary3 = (base_convert($WORD,16,2));      <------ shouldn't this give me that ^

[Barand]

These all have the same value

+------------+------------+------------+
|  Binary    |  Decimal   |   Hex      |
+------------+------------+------------+
|  10110001  |    177     |    B1      |
+------------+------------+------------+

In my code, setting $binary3 to any of these will give the same result
 

$binary3 = 0b10110001;

$binary3 = 177;

$binary3 = 0xB1;

 

[CyberLawrence]

10 hours ago, Barand said:

These all have the same value

+------------+------------+------------+
|  Binary    |  Decimal   |   Hex      |
+------------+------------+------------+
|  10110001  |    177     |    B1      |
+------------+------------+------------+

$binary3 = 0b10110001;

$binary3 = 177;

$binary3 = 0xB1;

In my code, setting $binary3 to any of these will give the same result
 

 

Correct, I am aware that all those numbers are the same just in different number bases. My issue is the data coming from the HTML Form is not numeric. I convert it to binary from what I receive as HEX in text format.

The variable $binary3 will never be the same number.... so it has to be a variable. Your code works great for manually entering the binary code.

AH HA! Got it. I don't need to convert it to binary. I just convert it to decimal and use your code to "strip" the bits out of the decimal number!

Thumbs up to you sir!

I was converting to binary to see if my code was working correctly and got stuck on that....

Thanks to all!

[Barand]

31 minutes ago, CyberLawrence said:

AH HA! Got it.

Well done.

For the record...

$input = 'B1';                                     // hex iput

$decimal = base_convert($input, 16, 10);           // convert to 177
for ($k=0; $k<8; $k++) {
    $vars[$k]  = ($decimal & 2**$k) ? 1:0;
} 

 

[requinix]

I was thinking base_convert 16->2 + str_split...

[Barand]

Good thinking, Batman!

$vars = array_reverse(str_split(base_convert($input, 16, 2)));