PHP Warning: pack(): Type h: illegal hex digit - line 37

Question

Hi everyone i'm trying to make a script that can encode & decode FSK Frequency-shift keying

the problem i'm have so far is PHP Warning: pack(): Type h: illegal hex digit - line 37

here is my code

$RATE = 44100;
$maxVol = pow(2,15)-1.0;
$data = "";

for ($x=0; $x<=$RATE*3; $x++){


    $vv = $maxVol*sin(2*pi()*$x*500/$RATE); #500Hz
    $data+=pack('h',$vv);  #this is line 37

}

echo $data;

pack in php seems like it does not support negative number & floats can someone please help me figure this out

Answer 1

The h format code specifies input as a hex string. It's hard to tell this from the error, but the - between the words digit and line is literally the character that is causing the error (i.e. it's not a separator in the message).

PHP Warning: pack(): Type h: illegal hex digit - line 37
                                               ^

In other words, your input is interpreted as a string containing the - character, which is not a legal hex digit (0123456789abcdef).

It's hard to give any specific advice on solving your problem without more information. At the very least, you need to review PHP's implementation of pack.