Tutorial :PHP function to create 8 chars long hash ([a-z] = no numbers allowed)


I need PHP function that will create 8 chars long [a-z] hash from any input string. So e.g. when I'll submit "Stack Overflow" it will return e.g. "gdqreaxc" (8 chars [a-z] no numbers allowed)


Perhaps something like:

$hash = substr(strtolower(preg_replace('/[0-9_\/]+/','',base64_encode(sha1($input)))),0,8);  

This produces a SHA1 hash, base-64 encodes it (giving us the full alphabet), removes non-alpha chars, lowercases it, and truncates it.

For $input = 'yar!';:


For $input = 'yar!!';:


So the spread seems pretty good.


This function will generate a hash containing evenly distributed characters [a-z]:

function my_hash($string, $length = 8) {        // Convert to a string which may contain only characters [0-9a-p]      $hash = base_convert(md5($string), 16, 26);        // Get part of the string      $hash = substr($hash, -$length);        // In rare cases it will be too short, add zeroes      $hash = str_pad($hash, $length, '0', STR_PAD_LEFT);        // Convert character set from [0-9a-p] to [a-z]      $hash = strtr($hash, '0123456789', 'qrstuvwxyz');        return $hash;  }  

By the way, if this is important for you, for 100,000 different strings you'll have ~2% chance of hash collision (for a 8 chars long hash), and for a million of strings this chance rises up to ~90%, if my math is correct.


function md5toabc($myMD5)  {     $newString = "";     for ($i = 0; $i < 16; $i+=2)     {          //add the first val of 0-15 to the second val of 0-15 for a range of 0-30            $myintval = hexdec(substr($myMD5, $i, $i +1) )  +                       hexdec(substr($myMD5, $i+1, $i +2) );          // mod by 26 and add 97 to get to the lowercase ascii range                  $newString .= chr(($myintval%26) + 97);     }     return $newString;  }  

Note this introduces bias to various characters, but do with it what you will. (Like when you roll two dice, the most common value is a 7 combined...) plus the modulo, etc...


one can give you a good a-p{8} (but not a-z) by using and modifying (the output of) a well known algo:

function mini_hash( $string )  {    $h = hash( 'crc32' , $string );    for($i=0;$i<8;$i++) {      $h{$i} = chr(96+hexdec($h{$i}));    }    return $h;  }  

interesting set of constraints you posted there


how about

substr (preg_replace(md5($mystring), "/[1-9]/", ""), 0, 8 );  

you could add a bit more entorpy by doing a

preg_replace($myString, "1", "g");  preg_replace($myString, "2", "h");  preg_replace($myString, "3", "i");  

etc instead of stripping the digits.

Note:If u also have question or solution just comment us below or mail us on toontricks1994@gmail.com
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