Digital Human Digital Human - 1 year ago 72
PHP Question

PHP bytearray to binary data

I have:

$my_a = array(100, 0, 13, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0);

Which is a byte-array which I want to convert to binary data to use with encryption. What I do is:

$bin_data = pack("C*", $my_a);

To validate if this is correct I reverse it by:

unpack("C*", $bin_data);

Problem is, I never get back the byte_array. What am I doing wrong?

Answer Source

pack() can't take a single array argument, unfortunately. You need to unpack the array into additional arguments.

You can use the following instead:

$packed = call_user_func_array("pack", array_merge(array("C*"), $my_a));

This will basically merge the packing argument with your data array and the function call_user_func_array() will call pack() with all arguments extracted from the given array, as single arguments, like needed.

Or alternatively use the splat operator if you're using PHP 5.6+

$packed = pack('C*', ...$my_a);

From the manual: Arrays and Traversable objects can be unpacked into argument lists when calling functions by using the ... operator. This is also known as the splat operator in other languages, including Ruby.

So the array is unpacked into single arguments, just like it is needed by pack().