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?

Answer 1

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.

Answer 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.