How do I send the binary representation through a PHP socket?

Question

I'm trying to send the binary representation of data through a PHP socket.

So if the number was 15, socket_write would send 00001111 as binary representation for 15.

How should I do this?

The amazing part is, at the interface layer, it gets sent as binary anyway! No need to convert. :D — mishmash
– mishmash, Commented Jan 14, 2013 at 7:07
@vanneto if you socket_write($fp, 15) it will be same as socket_write($fp, "15"), I.E. send the bytes 0x31 0x35 whereas as far as I can see he wants to send one byte 0x0F — Esailija
– Esailija, Commented Jan 14, 2013 at 7:09
Yeah, sorry for being confusing. I want to send the single byte representation of the data. I was doing socket_write($sock, 15) and it was sending the two bytes, which was confusing me. — Mitchell M
– Mitchell M, Commented Jan 14, 2013 at 7:25

Esailija · Accepted Answer · 2013-01-14 07:11:14Z

4

Use the chr function:

socket_write( $fp, chr(15));

You can also use \x escapes with hex values:

socket_write( $fp, "\xff\xff\xff\xff" );

Would send 4 bytes, with values 255 on each.

answered Jan 14, 2013 at 7:06

Esailija

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Comments

Koraktor · Accepted Answer · 2013-01-14 07:11:29Z

2

To generate a binary representation from arbitrary data use the pack() function.

Example:

$data = pack("v", 15); // "i" is unsigned little endian integer
socket_write($socket, $data);

See the manual page for more information on the various formats. There's also unpack() for the reverse functionality.

answered Jan 14, 2013 at 7:11

Koraktor

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this will send 0x0F 0x00, you want "C" to just send 0x0F

Well, that's the correct binary representation for an unsigned little endian 16 bit integer. Additionally C is not valid for numbers > 255.