I'm getting confused on how to do a simple thing, perhaps someone can help me.
At one point of my code I convert a bit array with 10 alarms (0 or 1) to a decimal and save it.
At another point I load the decimal and want to convert it back to a bit array.
This works however the bit array should be always have a length of 10 even if the decimal length is not 10 bites.
See my code:
// Convert array to dec:
$alarms = array(0,0,1,0,0,0,1,0,0,0);
$str = implode("", $alarms);
$dec = bindec($str);
// Convert back to bit array:
$bin = decbin($dec);
echo $bin;
The result of this code is:
10001000
But should be:
0010001000
Thanks!
Here's an idea of how you might implement this.
<?php
// Input array of bits
$inBits = [0,0,1,0,0,0,1,0,0,0];
// Convert to decimal value
$value = bindec(implode('', $inBits));
// Convert back to string of 0/1, adding padding as needed.
$outBitStr = str_pad(decbin($value), count($inBits), '0', STR_PAD_LEFT);
var_dump(implode('', $inBits) === $outBitStr); // TRUE
Related
Im trying to do a php multiplication of two 32bit long hexadecimal valuey with PHP and it seems it is messing up this calculation, the same happens if i multiplicate it as decimal value.
The calculation is as example:
0xB5365D09 * 0xDEBC252C
Converting to decimal before with hexdec doesnt change anything.
The expected result should be 0x9DAA52EA21664A8C but PHPs result is 0x9DAA52EA21664800
Example:
<?php
$res = 0xB5365D09 * 0xDEBC252C;
echo dechex(intval($res));
?>
What i am doing wrong here?
PHP8.2 running on debian, 64bit AMD.
So, for others to find the answer:
Someone stated in the comments to my question, that the result is above the PHP_MAX_INT limit. So when PHP handle it as a FLOAT, there will be some precision of the result lost. I got it to work using bcmath. In my case, i didnt do math with the result any further so i grabbed some piece of code from here, and made a simple function which does what i need. Here you can see a minimum-example:
function bcmul_hex($h1, $h2) {
$dec = bcmul($h1, $h2);
$hex = '';
do {
$last = bcmod($dec, 16);
$hex = dechex($last).$hex;
$dec = bcdiv(bcsub($dec, $last), 16);
} while($dec>0);
return $hex;
}
echo bcmul_hex(0xB5365D09, 0xDEBC252C);
Here is a live example.
If you're trying to perform a mathematical operation on a hexadecimal value in PHP, you can use the hexdec function to convert the hexadecimal value to a decimal value, perform the operation, and then use the dechex function to convert the result back to a hexadecimal value.
Here's an example:
<?php
$hex1 = "B5365D09";
$hex2 = "DEBC252C";
// Convert hexadecimal values to decimal
$dec1 = hexdec($hex1);
$dec2 = hexdec($hex2);
// Perform multiplication operation
$result = $dec1 * $dec2;
// Convert result back to hexadecimal
$hex_result = dechex($result);
// Print result
echo "Result: $hex_result\n";
This code will output the result of the multiplication as a hexadecimal value.
I know this is a pretty silly question, but I don't know what to do.
I have an arbitrary binary number, say,
1001000000110010000000100100000010000011000000010001000001011000110000110000011100011100000011000000010010011000100000000000000100100000010110001100001000000111
I want to convert it to Base 64 using PHP - and every way I try gives me a different result. Even different online converters convert it differently:
http://home2.paulschou.net/tools/xlate/
http://convertxy.com/index.php/numberbases/
PHP's base_convert only works up to base36, and base64_encode expects a string.
What do I do?
UPDATE: I implemented the solution functions suggested by #binaryLV, and it did work well.
However, I compared the results to PHP's built-in base_convert. It turned out that base_convert to base36 returns shorter values that the custom base64 function! (And yes, I did prepend a '1' to all the binary numbers to ensure leading zeros aren't lost).
I have noticed, too, that base_convert is quite innacurate with large numbers. So I need is a function which works like base_convert, but accurately and, preferably, up to base 64.
Length of a string in example is 160. It makes me think that it holds info about 160/8 characters. So,
split string into parts, each part holds 8 binary digits and describes single character
convert each part into a decimal integer
build a string from characters, that are made from ASCII codes from 2nd step
This will work with strings with size n*8. For other strings (e.g., 12 binary digits) it will give unexpected results.
Code:
function bin2base64($bin) {
$arr = str_split($bin, 8);
$str = '';
foreach ( $arr as $binNumber ) {
$str .= chr(bindec($binNumber));
}
return base64_encode($str);
}
$bin = '1001000000110010000000100100000010000011000000010001000001011000110000110000011100011100000011000000010010011000100000000000000100100000010110001100001000000111';
echo bin2base64($bin);
Result:
kDICQIMBEFjDBxwMBJiAASBYwgc=
Here's also function for decoding it back to string of binary digits:
function base64bin($str) {
$result = '';
$str = base64_decode($str);
$len = strlen($str);
for ( $n = 0; $n < $len; $n++ ) {
$result .= str_pad(decbin(ord($str[$n])), 8, '0', STR_PAD_LEFT);
}
return $result;
}
var_dump(base64bin(bin2base64($bin)) === $bin);
Result:
boolean true
PHP has a built in base 64 encoding function, see documentation here. If you want the decimal value of the binary string first use bin2dec, there are similar functions for hexadecimals by the way. The documentation is your friend here.
[EDIT]
I might have misunderstood your question, if you want to convert between actual bases (base 2 and 64) use base_convert
$number = 1001000000110010000000100100000010000011000000010001000001011000110000110000011100011100000011000000010010011000100000000000000100100000010110001100001000000111;
echo base64_encode ($number);
This is if you want the exact string be converted into Base 64.
To convert a binary number (2 base) to a 64 base use the base_convert function.
$number = 1001000000110010000000100100000010000011000000010001000001011000110000110000011100011100000011000000010010011000100000000000000100100000010110001100001000000111;
base_convert ($number , 2, 64);
I'm trying to format specific numbers up to 8 decimals by deleting unnecessary zeros.
My actual code is:
rtrim(sprintf("%.8f", $upto_eight_decimals), '0')
It actually prevents to format a number as 0.00012 into 1.2E-4 or 0.00012000
However, with numbers integer such as 1 it gets converted into 1. but this point is not my expected result (I know because of rtrim deleting all zeros).
UPDATE: rtrim(rtrim(sprintf("%.8f", $upto_eight_decimals), '0'), '.') it looks like working
You can do it this way, Just use number_format:
$upto_eight_decimals = "0.0001200";
$out = number_format((float)$upto_eight_decimals, 8, '.', '');
echo preg_replace("/\.?0*$/",'',$out);
or
echo $out + 0;
This function returns a string.
This will work for you, let me know is it work or not.
Is there any function that easily echos an integer that is 15+ digits long?
The only way I've managed is like this:
$num = 123456789012345;
$num = number_format($num);
$num = str_replace(',', '', $num);
echo $num;
But even this way it is only accurate up to 17 digits. After the 16th digit the number isn't printed accurately (because as a float it starts getting inaccurate - see here).
EDIT: From the answers below I wrote ini_set('precision',40); and then echoed $num straight. All this did was to, simply put, not show the decimal point in the float number. And again after the 16th digit it starts getting inaccurate.
I also tried the other suggestion of changing it into an array and then iterating through it with str_split($num); and again the numbers were inaccurate from the 17th digit on!
The simplest solution would be to convert the integer into a string. I've tried:
$num = (string)$num;
//and
$num = strval($num);
But neither change anything and they act as if as they remained as an int??
My question is specifically why are the conversions into strings not working. Is there a way to turn the number into a string? Thanks
The only solution I can think of is changing the precision of floats in the php.ini
ini_set('precision', 25);
I don't know where you get those large numbers from, but I'd suggest a look into bc functions too!
The last thing I thought of is using the explode function to split the string into an array and interate through it.
EDIT: When all suggestions failed, your only choices are to check out the BC Math and/or GMP functions as well as MoneyMath. The BigInteger package should also do the trick, which uses GMP and BC.
Well, you see, it's not an "int" as you claimed :)
echo PHP_INT_MAX; // echoes 9223372036854775807
$n = 9223372036854775807;
echo $n; // echoes 9223372036854775807
$n = 9223372036854775808;
echo $n; // echoes 9.2233720368548E+18
Setting precision to something greater, as manniL said, does the trick.
ini_set("precision", 50);
$n = 9223372036854775808;
echo $n; // echoes 9223372036854775808
I know this is a pretty silly question, but I don't know what to do.
I have an arbitrary binary number, say,
1001000000110010000000100100000010000011000000010001000001011000110000110000011100011100000011000000010010011000100000000000000100100000010110001100001000000111
I want to convert it to Base 64 using PHP - and every way I try gives me a different result. Even different online converters convert it differently:
http://home2.paulschou.net/tools/xlate/
http://convertxy.com/index.php/numberbases/
PHP's base_convert only works up to base36, and base64_encode expects a string.
What do I do?
UPDATE: I implemented the solution functions suggested by #binaryLV, and it did work well.
However, I compared the results to PHP's built-in base_convert. It turned out that base_convert to base36 returns shorter values that the custom base64 function! (And yes, I did prepend a '1' to all the binary numbers to ensure leading zeros aren't lost).
I have noticed, too, that base_convert is quite innacurate with large numbers. So I need is a function which works like base_convert, but accurately and, preferably, up to base 64.
Length of a string in example is 160. It makes me think that it holds info about 160/8 characters. So,
split string into parts, each part holds 8 binary digits and describes single character
convert each part into a decimal integer
build a string from characters, that are made from ASCII codes from 2nd step
This will work with strings with size n*8. For other strings (e.g., 12 binary digits) it will give unexpected results.
Code:
function bin2base64($bin) {
$arr = str_split($bin, 8);
$str = '';
foreach ( $arr as $binNumber ) {
$str .= chr(bindec($binNumber));
}
return base64_encode($str);
}
$bin = '1001000000110010000000100100000010000011000000010001000001011000110000110000011100011100000011000000010010011000100000000000000100100000010110001100001000000111';
echo bin2base64($bin);
Result:
kDICQIMBEFjDBxwMBJiAASBYwgc=
Here's also function for decoding it back to string of binary digits:
function base64bin($str) {
$result = '';
$str = base64_decode($str);
$len = strlen($str);
for ( $n = 0; $n < $len; $n++ ) {
$result .= str_pad(decbin(ord($str[$n])), 8, '0', STR_PAD_LEFT);
}
return $result;
}
var_dump(base64bin(bin2base64($bin)) === $bin);
Result:
boolean true
PHP has a built in base 64 encoding function, see documentation here. If you want the decimal value of the binary string first use bin2dec, there are similar functions for hexadecimals by the way. The documentation is your friend here.
[EDIT]
I might have misunderstood your question, if you want to convert between actual bases (base 2 and 64) use base_convert
$number = 1001000000110010000000100100000010000011000000010001000001011000110000110000011100011100000011000000010010011000100000000000000100100000010110001100001000000111;
echo base64_encode ($number);
This is if you want the exact string be converted into Base 64.
To convert a binary number (2 base) to a 64 base use the base_convert function.
$number = 1001000000110010000000100100000010000011000000010001000001011000110000110000011100011100000011000000010010011000100000000000000100100000010110001100001000000111;
base_convert ($number , 2, 64);