note 60312 added to function.decbin

It occured to me there must be a simple way to produce binary numbers from decimal ones with any number of bits, here's my attempt at a decimal to extended binary function. I hope the comments make it clear: <?php function decextbin($decimalnumber,$bit) { /* decextbin function by James Preece (j.preece@gmail.com) http://www.lovingit.co.uk Please feel free to use this function. If you find if useful I would love to hear from you. */ /* Function to return a binary number with as many bits as are requested... This works on the following principal. A binary number represents a figure 2,4,8,16 etc. If we work from the top down we can determine if a number contains each figure as a fraction and then work with what remains. For example, if we wish to display the number 10 as a 4 bit number we first discover the figure of the maximum bit by doubling four times: 1 2 4 8 The maxiumum figure is 8. Next we work down the figures: 8 goes in to 10 so the first digit is 1 leaving 2 4 does not go in to 2 so the second digit is 0 2 goes in to 2 so the third digit is 1 1 does not go in to 0 so the fourth digit is 0 Output: 1010 Now for the actual code! First we find that maximum value represented by the leftmost binary digit. For error checking purposes we also calulate the maximum number we can display using the number of bits requested: */ $maxval = 1; $sumval = 1; for($i=1;$i<$bit;$i++) { $maxval = $maxval * 2; $sumval = $sumval + $maxval; } /* Using our sumval we now check if it is possible to display the decimal number our function received: */ if ($sumval < $decimalnumber) return 'ERROR - Not enough bits to display this figure in binary.'; /* Then we work down through the figures, to get a better idea of how this works remove the commenting from the echo lines */ for($bitvalue=$maxval;$bitvalue>=1;$bitvalue=$bitvalue/2) { //echo 'Bit Value: '.$bitvalue.'<br />'; //echo 'Decimal Number: '.$decimalnumber.'<br />'; if (($decimalnumber/$bitvalue) >= 1) $thisbit = 1; else $thisbit = 0; //echo 'This Bit: '.$thisbit.'<br /><br />'; if ($thisbit == 1) $decimalnumber = $decimalnumber - $bitvalue; $binarynumber .= $thisbit; } /* Finally we return the output... */ return $binarynumber; } ?> An example usage might be like so: <?php for ($i = 0;$i<=8;$i++) { echo decextbin($i,4).'<br />'; } ?> Output: 0000 0001 0010 0011 0100 0101 0110 0111 1000 No need for padding or anything - also goes way over 32 bits. Huzzah. I suspect its limited by the maximum string length in php. Hmmm - Not sure what that is. ---- Manual Page -- http://www.php.net/manual/en/function.decbin.php Edit -- http://master.php.net/manage/user-notes.php?action=edit+60312 Delete: added to the manual -- http://master.php.net/manage/user-notes.php?action=delete+60312&report=yes&reason=added+to+the+manual Delete: bad code -- http://master.php.net/manage/user-notes.php?action=delete+60312&report=yes&reason=bad+code Delete: spam -- http://master.php.net/manage/user-notes.php?action=delete+60312&report=yes&reason=spam Delete: useless -- http://master.php.net/manage/user-notes.php?action=delete+60312&report=yes&reason=useless Delete: non-english -- http://master.php.net/manage/user-notes.php?action=delete+60312&report=yes&reason=non-english Delete: already in docs -- http://master.php.net/manage/user-notes.php?action=delete+60312&report=yes&reason=already+in+docs Delete: other reasons -- http://master.php.net/manage/user-notes.php?action=delete+60312&report=yes Reject -- http://master.php.net/manage/user-notes.php?action=reject+60312&report=yes Search -- http://master.php.net/manage/user-notes.php