strange Bitwise results

[Dizzee]

Hi I've been playing with the bitwise operator and some binary and have hit a wall

 

the code should work , but it stops working when the number gets to 10 digits long or more

I've created the following to demonstrate

could someone please explain why it is doing this and possably how to fix it

thanks

 

 

<?php
print_r($_POST);
if (!$_POST['role']) {
$myroles = "72057594037927808";
$my_lengh = 9;
} else {
$myroles = $_POST['role'];
$my_lengh = $_POST['mylengh'];
}
?>
<form action="" method="post">
    <p>Number: 
      <input type="text" name="role" value="<?php echo $myroles; ?>" />
      <br />truncate to:
      <input name="mylengh" type="text" value="<?php echo $my_lengh; ?>" size="2" maxlength="2"/>
      <br />
      <input type="submit" name="submit" value="Submit me!" />
  </p>
</form>
<?php
echo "<hr>";

echo "role number = $myroles<p>";
$roles = substr($myroles, 0-$my_lengh, $my_lengh);
echo "Used number = $roles<p>";

if ($roles & 1) {

echo "bitwise 2<sup>0</sup><BR>";
}

if ($roles & (128)) {
echo "bitwise 2<sup>7</sup><BR>";
}

if ($roles & (256)) {
echo "bitwise 2<sup>8</sup><BR>";
}

if ($roles & (512)) {
echo "bitwise 2<sup>9</sup><BR>";
}

if ($roles & (1024)) {
echo "bitwise 2<sup>10</sup><BR>";
}

if ($roles & (2048)) {
echo "bitwise 2<sup>11</sup><BR>";
}

if ($roles & (4096)) {
echo "bitwise 2<sup>12</sup><BR>";
}

if ($roles & (8192)) {
echo "bitwise 2<sup>13</sup><BR>";
}

if ($roles & (16384)) {
echo "bitwise 2<sup>14</sup><BR>";
}

if ($roles & (32768)) {
echo "bitwise 2<sup>15</sup><BR>";
}

if ($roles & (65536)) {
echo "bitwise 2<sup>16</sup><BR>";
}

if ($roles & (131072)) {
echo "bitwise 2<sup>17</sup><BR>";
}

if ($roles & (262144)) {
echo "bitwise 2<sup>18</sup><BR>";
}

if ($roles & (524288)) {
echo "bitwise 2<sup>19</sup><BR>";
}

if ($roles & (1048576)) {
echo "bitwise 2<sup>20</sup><BR>";
}

if ($roles & (2097152)) {
echo "bitwise 2<sup>21</sup><BR>";
}

if ($roles & (4194304)) {
echo "bitwise 2<sup>22</sup><BR>";
}

if ($roles & (8388608)) {
echo "bitwise 2<sup>23</sup><BR>";
}

if ($roles & (16777216)) {
echo "bitwise 2<sup>24</sup><BR>";
}

if ($roles & (33554432)) {
echo "bitwise 2<sup>25</sup><BR>";
}

if ($roles & (67108864)) {
echo "bitwise 2<sup>26</sup><BR>";
}

if ($roles & (134217728)) {
echo "bitwise 2<sup>27</sup><BR>";
}

if ($roles & (268435456)) {
echo "bitwise 2<sup>28</sup><BR>";
}

if ($roles & (536870912)) {
echo "bitwise 2<sup>29</sup><BR>";
}

if ($roles & (1073741824)) {
echo "bitwise 2<sup>30</sup><BR>";
}

if ($roles & (2147483648)) {
echo "bitwise 2<sup>31</sup><BR>";
}

if ($roles & (4294967296)) {
echo "bitwise 2<sup>32</sup><BR>";
}

if ($roles & (8589934592)) {
echo "bitwise 2<sup>33</sup><BR>";
}

if ($roles & (17179869184)) {
echo "bitwise 2<sup>34</sup><BR>";
}

if ($roles & (34359738368)) {
echo "bitwise 2<sup>35</sup><BR>";
}

if ($roles & (68719476736)) {
echo "bitwise 2<sup>36</sup><BR>";
}

if ($roles & (137438953472)) {
echo "bitwise 2<sup>37</sup><BR>";
}

if ($roles & (274877906944)) {
echo "bitwise 2<sup>38</sup><BR>";
}

if ($roles & (549755813888)) {
echo "bitwise 2<sup>39</sup><BR>";
}

if ($roles & (1099511627776)) {
echo "bitwise 2<sup>40</sup><BR>";
}

if ($roles & (2199023255552)) {
echo "bitwise 2<sup>41</sup><BR>";
}
?>

[btherl]

Try the following script:

 

<?
foreach (range(0,40) as $pow) {
  print "2^$pow = " . intval(pow(2,$pow)) . "\n";
}
?>

 

If your php uses 32 bit integers, you should see it fail at 2^31.

[btherl]

FYI, here is the output on a 64 bit php:

 

2^0 = 1
2^1 = 2
2^2 = 4
2^3 = 8
2^4 = 16
2^5 = 32
2^6 = 64
2^7 = 128
2^8 = 256
2^9 = 512
2^10 = 1024
2^11 = 2048
2^12 = 4096
2^13 = 8192
2^14 = 16384
2^15 = 32768
2^16 = 65536
2^17 = 131072
2^18 = 262144
2^19 = 524288
2^20 = 1048576
2^21 = 2097152
2^22 = 4194304
2^23 = 8388608
2^24 = 16777216
2^25 = 33554432
2^26 = 67108864
2^27 = 134217728
2^28 = 268435456
2^29 = 536870912
2^30 = 1073741824
2^31 = 2147483648
2^32 = 4294967296
2^33 = 8589934592
2^34 = 17179869184
2^35 = 34359738368
2^36 = 68719476736
2^37 = 137438953472
2^38 = 274877906944
2^39 = 549755813888
2^40 = 1099511627776

 

That'll give you at least 63 bits to play with (and the 64th too if you are careful with it).  But again there is a hard limit based on the size of an integer.

[Dizzee]

Yup, thanks I see the problem now, If I remove intval I get the correct return?

I've been searching but can't find a work around, the best I found was for Xor

function unsigned_xor32 ($a, $b)
{
        $a1 = $a & 0x7FFF0000;
        $a2 = $a & 0x0000FFFF;
        $a3 = $a & 0x80000000;
        $b1 = $b & 0x7FFF0000;
        $b2 = $b & 0x0000FFFF;
        $b3 = $b & 0x80000000;

        $c = ($a3 != $b3) ? 0x80000000 : 0;

        return (($a1 ^ $b1) |($a2 ^ $b2)) + $c;
}

I'm looking at dealing with it, but any points in the right direction would be appreciated,

I'm thinking either converting from a float or converting to hex??