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I am looking for the shortest way to generate random/unique strings and for that I was using the following two:
$cClass = sha1(time());
or
$cClass = md5(time());
However, I need the string to begin with a letter, I was looking at base64 encoding but that adds == at the end and then I would need to get rid of that.
What would be the best way to achieve this with one line of code?
Update:
PRNDL came up with a good suggestions which I ended up using it but a bit modified
echo substr(str_shuffle(abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ),0, 1) . substr(str_shuffle(aBcEeFgHiJkLmNoPqRstUvWxYz0123456789),0, 31)
Would yield 32 characters mimicking the md5 hash but it would always product the first char an alphabet letter, like so;
However, Uours really improved upon and his answer;
substr(str_shuffle("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"), 0, 1).substr(md5(time()),1);
is shorter and sweeter
The other suggestion by Anonymous2011 was very awesome but the first character for some reason would always either M, N, Y, Z so didn't fit my purposes but would have been the chosen answer, by the way does anyone know why it would always yield those particular letters?
Here is the preview of my modified version
echo rtrim(base64_encode(md5(microtime())),"=");
Rather than shuffling the alphabet string , it is quicker to get a single random char .
Get a single random char from the string and then append the md5( time( ) ) to it . Before appending md5( time( ) ) remove one char from it so as to keep the resulting string length to 32 chars :
substr("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ", mt_rand(0, 51), 1).substr(md5(time()), 1);
Lowercase version :
substr("abcdefghijklmnopqrstuvwxyz", mt_rand(0, 25), 1).substr(md5(time()), 1);
Or even shorter and a tiny bit faster lowercase version :
chr(mt_rand(97, 122)).substr(md5(time()), 1);
/* or */
chr(mt_rand(ord('a'), ord('z'))).substr(md5(time()), 1);
A note to anyone trying to generate many random strings within a second: Since time( ) returns time in seconds , md5( time( ) ) will be same throughout a given second-of-time due to which if many random strings were generated within a second-of-time, those probably could end up having some duplicates .
I have tested using below code . This tests lower case version :
$num_of_tests = 100000;
$correct = $incorrect = 0;
for( $i = 0; $i < $num_of_tests; $i++ )
{
$rand_str = substr( "abcdefghijklmnopqrstuvwxyz" ,mt_rand( 0 ,25 ) ,1 ) .substr( md5( time( ) ) ,1 );
$first_char_of_rand_str = substr( $rand_str ,0 ,1 );
if( ord( $first_char_of_rand_str ) < ord( 'a' ) or ord( $first_char_of_rand_str ) > ord( 'z' ) )
{
$incorrect++;
echo $rand_str ,'<br>';
}
else
{
$correct++;
}
}
echo 'Correct: ' ,$correct ,' . Incorrect: ' ,$incorrect ,' . Total: ' ,( $correct + $incorrect );
I had found something like this:
$length = 10;
$randomString = substr(str_shuffle(md5(time())),0,$length);
echo $randomString;
If you need it to start with a letter, you could do this. It's messy... but it's one line.
$randomString = substr(str_shuffle("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"), 0, 1) . substr(str_shuffle("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"), 0, 10);
echo $randomString;
I decided this question needs a better answer. Like code golf! This also uses a better random byte generator.
preg_replace("/[\/=+]/", "", base64_encode(openssl_random_pseudo_bytes(8)));
Increase the number of bytes for a longer password, obviously.
Creates a 200 char long hexdec string:
$string = bin2hex(openssl_random_pseudo_bytes(100));
maaarghk's answer is better though.
base_convert(microtime(true), 10, 36);
You can try this:
function KeyGenerator($uid) {
$tmp = '';
for($z=0;$z<5;$z++) {
$tmp .= chr(rand(97,122)) . rand(0,100);
}
$tmp .= $uid;
return $tmp;
}
I have generated this code for you. Simple, short and (resonably) elegant.
This uses the base64 as you mentioned, if length is not important to you - However it removes the "==" using str_replace.
<?php
echo str_ireplace("==", "", base64_encode(time()));
?>
I use this function
usage:
echo randomString(20, TRUE, TRUE, FALSE);
/**
* Generate Random String
* #param Int Length of string(50)
* #param Bool Upper Case(True,False)
* #param Bool Numbers(True,False)
* #param Bool Special Chars(True,False)
* #return String Random String
*/
function randomString($length, $uc, $n, $sc) {
$rstr='';
$source = 'abcdefghijklmnopqrstuvwxyz';
if ($uc)
$source .= 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
if ($n)
$source .= '1234567890';
if ($sc)
$source .= '|##~$%()=^*+[]{}-_';
if ($length > 0) {
$rstr = "";
$length1= $length-1;
$input=array('a','b','c','d','e','f','g','h','i','j,''k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z')
$rand = array_rand($input, 1)
$source = str_split($source, 1);
for ($i = 1; $i <= $length1; $i++) {
$num = mt_rand(1, count($source));
$rstr1 .= $source[$num - 1];
$rstr = "{$rand}{$rstr1}";
}
}
return $rstr;
}
I'm using this one to generate dozens of unique strings in a single go, without repeating them, based on other good examples above:
$string = chr(mt_rand(97, 122))
. substr(md5(str_shuffle(time() . rand(0, 999999))), 1);
This way, I was able to generate 1.000.000 unique strings in ~5 seconds. It's not THAT fast, I know, but as I just need a handful of them, I'm ok with it. By the way, generating 10 strings took less than 0.0001 ms.
JavaScript Solution:
function randomString(pIntLenght) {
var strChars = “0123456789ABCDEFGHIJKLMNOPQRSTUVWXTZabcdefghiklmnopqrstuvwxyz”;
var strRandomstring = ”;
for (var intCounterForLoop=0; intCounterForLoop < pIntLenght; intCounterForLoop++) {
var rnum = Math.floor(Math.random() * strChars.length);
strRandomstring += strChars.substring(rnum,rnum+1);
}
return strRandomstring;
}
alert(randomString(20));
Reference URL : Generate random string using JavaScript
PHP Solution:
function getRandomString($pIntLength = 30) {
$strAlphaNumericString = ’0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ’;
$strReturnString = ”;
for ($intCounter = 0; $intCounter < $pIntLength; $intCounter++) {
$strReturnString .= $strAlphaNumericString[rand(0, strlen($strAlphaNumericString) - 1)];
}
return $strReturnString;
}
echo getRandomString(20);
Reference URL : Generate random String using PHP
This function returns random lowercase string:
function randomstring($len=10){
$randstr='';
for($iii=1; $iii<=$len; $iii++){$randstr.=chr(rand(97,122));};
return($randstr);
};
I find that base64 encoding is useful for creating random strings, and use this line:
base64_encode(openssl_random_pseudo_bytes(9));
It gives me a random string of 12 positions, with the additional benefit that the randomness is "cryptographically strong".
to generate strings consists of random characters, you can use this function
public function generate_random_name_for_file($length=50){
$key = '';
$keys = array_merge(range(0, 9), range('a', 'z'));
for ($i = 0; $i < $length; $i++) {
$key .= $keys[array_rand($keys)];
}
return $key;
}
It really depends on your requirements.
I needed strings to be unique between test runs, but not many other restrictions.
I also needed my string to start with a character, and this was good enough for my purpose.
$mystring = "/a" . microtime(true);
Example output:
a1511953584.0997
How to match the OPs original request in an awful way (expanded for readability):
// [0-9] ASCII DEC 48-57
// [A-Z] ASCII DEC 65-90
// [a-z] ASCII DEC 97-122
// Generate: [A-Za-z][0-9A-Za-z]
$r = implode("", array_merge(array_map(function($a)
{
$a = [rand(65, 90), rand(97, 122)];
return chr($a[array_rand($a)]);
}, array_fill(0, 1, '.')),
array_map(function($a)
{
$a = [rand(48, 57), rand(65, 90), rand(97, 122)];
return chr($a[array_rand($a)]);
}, array_fill(0, 7, '.'))));
One the last array_fill() would would change the '7' to your length - 1.
For one that does all alpha-nurmeric (And still slow):
// [0-9A-Za-z]
$x = implode("", array_map(function($a)
{
$a = [rand(48, 57), rand(65, 90), rand(97, 122)];
return chr($a[array_rand($a)]);
}, array_fill(0, 8, '.')));
The following one-liner meets the requirements in your question: notably, it begins with a letter.
substr("abcdefghijklmnop",random_int(0, 16),1) . bin2hex(random_bytes(15))
If you didn't care whether the string begins with a letter, you could just use:
bin2hex(random_bytes(16))
Note that here we use random_bytes and random_int, which were introduced in PHP 7 and use cryptographic random generators, something that is important if you want unique strings to be hard to guess. Many other solutions, including those involving time(), microtime(), uniqid(), rand(), mt_rand(), str_shuffle(), array_rand(), and shuffle(), are much more predictable and are unsuitable if the random string will serve as a password, a bearer credential, a nonce, a session identifier, a "verification code" or "confirmation code", or another secret value.
I also list other things to keep in mind when generating unique identifiers, especially random ones.
True one liner random string options:
implode('', array_rand(array_flip(str_split(str_shuffle('abcdefghijklmnopqrstuvwxyz1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ'))), 21));
md5(microtime() . implode('', array_rand(array_flip(str_split(str_shuffle('abcdefghijklmnopqrstuvwxyz1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ'))), 21)));
sha1(microtime() . implode('', array_rand(array_flip(str_split(str_shuffle('abcdefghijklmnopqrstuvwxyz1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ'))), 21)));
I came up with this function that truncates a given string to either the given number of words or the given number of characters whatever is shorter.
Then, after it chops off everything after the number of characters or words limit, it appends a '...' to the string.
How can I remove characters / words from the middle of the string and replace them with '...' instead of replacing characters / words at the end with the '...'?
Here is my code:
function truncate($input, $maxWords, $maxChars){
$words = preg_split('/\s+/', $input);
$words = array_slice($words, 0, $maxWords);
$words = array_reverse($words);
$chars = 0;
$truncated = array();
while(count($words) > 0)
{
$fragment = trim(array_pop($words));
$chars += strlen($fragment);
if($chars > $maxChars){
if(!$truncated){
$truncated[]=substr($fragment, 0, $maxChars - $chars);
}
break;
}
$truncated[] = $fragment;
}
$result = implode($truncated, ' ');
return $result . ($input == $result ? '' : '...');
}
For example if truncate('the quick brown fox jumps over the lazy dog', 8, 16); is called, 16 characters is shorter so that is the truncation that will happen. So, 'fox jumps over the lazy dog' will be removed and '...' will be appended.
But, instead, how can I have half of the character limit come from the beginning of string and half come from the end of string and what is removed in the middle replaced by '...'?
So, the string I'm looking to be return in this, one, case would be: 'the quic...lazy dog'.
$text = 'the quick brown fox jumps over the lazy dog';
$textLength = strlen($text);
$maxChars = 16;
$result = substr_replace($text, '...', $maxChars/2, $textLength-$maxChars);
$result is now:
the quic...lazy dog
This won't alter input which is shorter than $maxChars, and takes the length of the replacement ... into account:
function str_truncate_middle($text, $maxChars = 25, $filler = '...')
{
$length = strlen($text);
$fillerLength = strlen($filler);
return ($length > $maxChars)
? substr_replace($text, $filler, ($maxChars - $fillerLength) / 2, $length - $maxChars + $fillerLength)
: $text;
}
Here's what I ended up using:
/**
* Removes characters from the middle of the string to ensure it is no more
* than $maxLength characters long.
*
* Removed characters are replaced with "..."
*
* This method will give priority to the right-hand side of the string when
* data is truncated.
*
* #param $string
* #param $maxLength
* #return string
*/
function truncateMiddle($string, $maxLength)
{
// Early exit if no truncation necessary
if (strlen($string) <= $maxLength) return $string;
$numRightChars = ceil($maxLength / 2);
$numLeftChars = floor($maxLength / 2) - 3; // to accommodate the "..."
return sprintf("%s...%s", substr($string, 0, $numLeftChars), substr($string, 0 - $numRightChars));
}
For my use case the right-hand side of the string contained more useful information so this method is biased towards taking characters out of the left-hand half.
I have a string with, for example, 32 characters. For first, i want to establish that the string have max 32 characters and i want add blank spaces if characters is only, for example, 9.
Example:
ABCDEFGHI ---> 9 characters
I want this:
ABCDEFGHI_______________________ ---> 9 characters + 23 blank spaces added automatically.
The function you are looking for is str_pad.
http://php.net/manual/de/function.str-pad.php
$str = 'ABCDEFGHI';
$longstr = str_pad($str, 32);
The default pad string already is blank spaces.
As your maximum length should be 32 and str_pad won't take any action when the string is longer than 32 characters you might want to shorten it down using substr then:
http://de.php.net/manual/de/function.substr.php
$result = substr($longstr, 0, 32);
This again won't take any action if your string is exactly 32 characters long, so you always end up with a 32 characters string in $result now.
Use str_pad:
str_pad('ABCDEFGHI', 32);
Use str_pad function:
$result = str_pad($input, 32, " ");
you need str_pad
$padded = str_pad($in,32,' ');
You can have left or right padded, tons of options, check them all out here
If the input exceeds 32 chars, no action is taken, but that's an easy check to implement:
if (strlen($padded) > 32)
{
throw new Exception($padded.' is too long');//or some other action
}
If you want to do more customization inside the function you could use this
function fill($input, $length, $filler = ' ')
{
$len = strlen($input);
$diff = $length - $len;
if($diff > 0)
{
for ($i = 0; $i < $diff; $i++)
{
$input = $input . $filler;
}
}
return substr($input, 0, $length);
}
for($i=0;$i<(32-strlen($your_string));$i++)
{
$new_string.=$your_string.' '
}
hope that would be helpful for you
$str = "ABCDEFGHI";
for ($i = 0; $i < 23; $i++) {
$str .= " ";
}
This is what You want?
When saw other comments, then that will be the best solution.
i wanna get some field values from database and present them on html.
but some of them are longer than the div width so i wanted to chop if of and add 3 dots after them if they are longer than lets say 30 characthers.
windows vs mac os x-> windows vs m...
threads about windows vista -> threads about win...
how can i do that?
If you need to perform this kind of functionality more than once, consider this function:
function truncate($string, $limit, $break = '.', $pad = '...')
{
// return with no change if string is shorter than $limit
if(strlen($string) <= $limit) return $string;
// is $break present between $limit and the end of the string?
if(false !== ($breakpoint = strpos($string, $break, $limit)))
{
if($breakpoint < strlen($string) - 1)
{
$string = substr($string, 0, $breakpoint) . $pad;
}
}
return $string;
}
Usage:
echo truncate($string, 30);
Judging by your examples you don't seem to care about preserving words, so here it is:
if (strlen($str) > 30)
{
echo substr($str, 0, 30) . '...';
}
If you use Smarty, you can use the truncate modifier.
{myLongText|truncate:30:'...':true}
BTW, such kind of function should exist in any decent template engine.
Check out wordwrap(), that should be what you're looking for.
I know that the rand function in PHP generates random integers, but what is the best way to generate a random string such as:
Original string, 9 chars
$string = 'abcdefghi';
Example random string limiting to 6 chars
$string = 'ibfeca';
UPDATE: I have found tons of these types of functions, basically I'm trying to understand the logic behind each step.
UPDATE: The function should generate any amount of chars as required.
Please comment the parts if you reply.
If you want to allow repetitive occurences of characters, you can use this function:
function randString($length, $charset='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789')
{
$str = '';
$count = strlen($charset);
while ($length--) {
$str .= $charset[mt_rand(0, $count-1)];
}
return $str;
}
The basic algorithm is to generate <length> times a random number between 0 and <number of characters> − 1 we use as index to pick a character from our set and concatenate those characters. The 0 and <number of characters> − 1 bounds represent the bounds of the $charset string as the first character is addressed with $charset[0] and the last with $charset[count($charset) - 1].
Well, you didn't clarify all the questions I asked in my comment, but I'll assume that you want a function that can take a string of "possible" characters and a length of string to return. Commented thoroughly as requested, using more variables than I would normally, for clarity:
function get_random_string($valid_chars, $length)
{
// start with an empty random string
$random_string = "";
// count the number of chars in the valid chars string so we know how many choices we have
$num_valid_chars = strlen($valid_chars);
// repeat the steps until we've created a string of the right length
for ($i = 0; $i < $length; $i++)
{
// pick a random number from 1 up to the number of valid chars
$random_pick = mt_rand(1, $num_valid_chars);
// take the random character out of the string of valid chars
// subtract 1 from $random_pick because strings are indexed starting at 0, and we started picking at 1
$random_char = $valid_chars[$random_pick-1];
// add the randomly-chosen char onto the end of our string so far
$random_string .= $random_char;
}
// return our finished random string
return $random_string;
}
To call this function with your example data, you'd call it something like:
$original_string = 'abcdefghi';
$random_string = get_random_string($original_string, 6);
Note that this function doesn't check for uniqueness in the valid chars passed to it. For example, if you called it with a valid chars string of 'AAAB', it would be three times more likely to choose an A for each letter as a B. That could be considered a bug or a feature, depending on your needs.
My favorite:
echo substr(md5(rand()), 0, 7);
So, let me start off by saying USE A LIBRARY. Many exist:
RandomCompat
RandomLib
SecurityMultiTool
The core of the problem is almost every answer in this page is susceptible to attack. mt_rand(), rand(), lcg_value() and uniqid() are all vulnerable to attack.
A good system will use /dev/urandom from the filesystem, or mcrypt_create_iv() (with MCRYPT_DEV_URANDOM) or openssl_pseudo_random_bytes(). Which all of the above do. PHP 7 will come with two new functions random_bytes($len) and random_int($min, $max) that are also safe.
Be aware that most of those functions (except random_int()) return "raw strings" meaning they can contain any ASCII character from 0 - 255. If you want a printable string, I'd suggest running the result through base64_encode().
function generate_random_string($name_length = 8) {
$alpha_numeric = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
return substr(str_shuffle(str_repeat($alpha_numeric, $name_length)), 0, $name_length);
}
Updated the code as per mzhang's great suggestion in the comments below.
A better and updated version of #taskamiski's excellent answer:
Better version, using mt_rand() instead of rand():
echo md5(mt_rand()); // 32 char string = 128bit
Even better, for longer strings, using the hash() function that allows to select hashing algorithmns:
echo hash('sha256', mt_rand()); // 64 char string
echo hash('sha512', mt_rand()); // 128 char string
If you want to cut the result down to let's say 50 chars, do it like this:
echo substr(hash('sha256', mt_rand()), 0, 50); // 50 char string
Joining characters at the end should be more efficient that repeated string concatenation.
Edit #1: Added option to avoid character repetition.
Edit #2: Throws exception to avoid getting into infinite loop if $norepeat is selected and $len is greater than the charset to pick from.
Edit #3: Uses array keys to store picked random characters when $norepeat is selected, as associative array key lookup is faster than linearly searching the array.
function rand_str($len, $norepeat = true)
{
$chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
$max = strlen($chars) - 1;
if ($norepeat && len > $max + 1) {
throw new Exception("Non repetitive random string can't be longer than charset");
}
$rand_chars = array();
while ($len) {
$picked = $chars[mt_rand(0, $max)];
if ($norepeat) {
if (!array_key_exists($picked, $rand_chars)) {
$rand_chars[$picked] = true;
$len--;
}
}
else {
$rand_chars[] = $picked;
$len--;
}
}
return implode('', $norepeat ? array_keys($rand_chars) : $rand_chars);
}
this will generate random string
function generateRandomString($length=10) {
$original_string = array_merge(range(0,9), range('a','z'), range('A', 'Z'));
$original_string = implode("", $original_string);
return substr(str_shuffle($original_string), 0, $length);
}
echo generateRandomString(6);
I think I will add my contribution here as well.
function random_string($length) {
$bytes_1 = openssl_random_pseudo_bytes($length);
$hex_1 = bin2hex($bytes_1);
$random_numbers = substr(sha1(rand()), 0, $length);
$bytes_2 = openssl_random_pseudo_bytes($length);
$hex_2 = bin2hex($bytes_2);
$combined_chars = $hex_1 . $random_numbers . $hex_2;
$chars_crypted = hash('sha512', $combined_chars);
return $chars_crypted;
}
Thanks
Most aspects of this have already been discussed, but i'd recommend a slight update:
If you are using this for retail usage, I would avoid the domain
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789
and instead use:
ABCDEFGHJKMNPQRSTUVWXY3456789
Granted, you end up with far fewer characters, but it saves a great deal of hassle, as customers cannot mistake 0 for O, or 1 for l or 2 for Z. Also, you can do an UPPER on the input and customers can then enter upper or lower case letters -- that is also sometimes confusing since they can look similar.
What do you need a random string for?
Is this going to be used for anything remotely analogous to a password?
If your random string requires any security properties at all, you should use PHP 7's random_int() function instead of all the insecure mt_rand() answers in this thread.
/**
* Generate a random string
*
* #link https://paragonie.com/b/JvICXzh_jhLyt4y3
*
* #param int $length - How long should our random string be?
* #param string $charset - A string of all possible characters to choose from
* #return string
*/
function random_str($length = 32, $charset = 'abcdefghijklmnopqrstuvwxyz')
{
// Type checks:
if (!is_numeric($length)) {
throw new InvalidArgumentException(
'random_str - Argument 1 - expected an integer'
);
}
if (!is_string($charset)) {
throw new InvalidArgumentException(
'random_str - Argument 2 - expected a string'
);
}
if ($length < 1) {
// Just return an empty string. Any value < 1 is meaningless.
return '';
}
// This is the maximum index for all of the characters in the string $charset
$charset_max = strlen($charset) - 1;
if ($charset_max < 1) {
// Avoid letting users do: random_str($int, 'a'); -> 'aaaaa...'
throw new LogicException(
'random_str - Argument 2 - expected a string at least 2 characters long'
);
}
// Now that we have good data, this is the meat of our function:
$random_str = '';
for ($i = 0; $i < $length; ++$i) {
$r = random_int(0, $charset_max);
$random_str .= $charset[$r];
}
return $random_str;
}
If you aren't on PHP 7 yet (which is probably the case, as it hasn't been released as of this writing), then you'll want paragonie/random_compat, which is a userland implementation of random_bytes() and random_int() for PHP 5 projects.
For security contexts, always use random_int(), not rand(), mt_rand(), etc. See ircmaxell's answer as well.
built on top of https://stackoverflow.com/a/853898/533426
but with php 7 cryptographically secure random function and lower AND upper case alphabet
function random($length = 8){
$valid_chars ="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
// start with an empty random string
$random_string = "";
// count the number of chars in the valid chars string so we know how many choices we have
$num_valid_chars = strlen($valid_chars);
// repeat the steps until we've created a string of the right length
for ($i = 0; $i < $length; $i++)
{
// pick a random number from 1 up to the number of valid chars
$random_pick = random_int(1, $num_valid_chars);
// take the random character out of the string of valid chars
// subtract 1 from $random_pick because strings are indexed starting at 0, and we started picking at 1
$random_char = $valid_chars[$random_pick-1];
// add the randomly-chosen char onto the end of our string so far
$random_string .= $random_char;
}
// return our finished random string
return $random_string;
}
//example output XjdXHakZ, yBG8hpZG, L6jg4FpK
// #author http://codeascraft.etsy.com/2012/07/19/better-random-numbers-in-php-using-devurandom/
function devurandom_rand($min = 0, $max = 0x7FFFFFFF)
{
$diff = $max - $min;
if ($diff < 0 || $diff > 0x7FFFFFFF) {
throw new RuntimeException('Bad range');
}
$bytes = mcrypt_create_iv(4, MCRYPT_DEV_URANDOM);
if ($bytes === false || strlen($bytes) != 4) {
throw new RuntimeException('Unable to get 4 bytes');
}
$ary = unpack('Nint', $bytes);
$val = $ary['int'] & 0x7FFFFFFF; // 32-bit safe
$fp = (float) $val / 2147483647.0; // convert to [0,1]
return round($fp * $diff) + $min;
}
function build_token($length = 60, $characters_map = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789') {
$map_length = mb_strlen($characters_map)-1;
$token = '';
while ($length--) {
$token .= mb_substr($characters_map, devurandom_rand(0,$map_length),1);
}
return $token;
}
This will work only in UNIX environment where PHP is compiled with mcrypt.
Do you want to create your password by a random permutation of the original letters? Should it just contain unique characters?
Use rand to choose random letters by index.
This is an old question but I want try to post my solution... I always use this my function to generate a custom random alphanumeric string...
<?php
function random_alphanumeric($length) {
$chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ12345689';
$my_string = '';
for ($i = 0; $i < $length; $i++) {
$pos = mt_rand(0, strlen($chars) -1);
$my_string .= substr($chars, $pos, 1);
}
return $my_string;
}
$test = random_alphanumeric(50); // 50 characters
echo $test;
?>
test: UFOruSSTCPIqxTRIIMTRkqjOGidcVlhYaS9gtwttxglheVugFM
if you need two or more unique strings you can use this trick...
$string_1 = random_alphanumeric(50);
$string_2 = random_alphanumeric(50);
while ($string_1 == $string_2) {
$string_1 = random_alphanumeric(50);
$string_2 = random_alphanumeric(50);
if ($string_1 != $string_2) {
break;
}
}
echo $string_1;
echo "<br>\n";
echo $string_2;
$string_1: tMYicqLCHEvENwYbMUUVGTfkROxKIekEB2YXx5FHyVByp3mlJO
$string_2: XdMNJYpMlFRKFDlF6GhVn6jsBVNQ1BCCevj8yK2niFOgpDI2MU
I hope this help.
echo substr(bin2hex(random_bytes(14)), 0, $length);
this code gets a random bytes, that are converted from binary to hexadecimal, and then takes a substring of this hexadecimal string, as long you puts in $length variable
Try this
Simple enough!
function RandomFromCharset($charset,$length)
{
$characters = $charset; // your existing charset / defined string
$charactersLength = strlen($characters);
$random_from_charset = '';
for ($i = 0; $i < $length; $i++)
{
$random_from_charset.= $characters[rand(0, $charactersLength - 1)];
}
return random_from_charset;
}
Call the function as follows
RandomFromCharset($charset,$length);
where $length will be length of random string you want (this can be predefined also in the function as RandomFromCharset(charset,$length=10) ) to generate and $charset will be your existing string to which you want to restrict the characters.
One approach is to generate an md5 from a random number and extract the number of characters you want:
<?php
$random = substr(md5(mt_rand()), 0, 7);
echo $random;
?>
mt_rand will generate a random number, md5 will create a 32 character string (containing both letters and numbers) and, in this example, we're extracting the first 7 characters of text.
you could make an array of characters then use rand() to pick a letter from the array and added it to a string.
$letters = array( [0] => 'a' [1] => 'b' [2] => 'c' [3] => 'd' ... [25] = 'z');
$lengthOfString = 10;
$str = '';
while( $lengthOfString-- )
{
$str .= $letters[rand(0,25)];
}
echo $str;
*note that this does allow repeat characters
This builds on Gumbo's solution by adding functionality to list a set of characters to be skipped in the base character set. The random string selects characters from $base_charset which do not also appear in $skip_charset.
/* Make a random string of length using characters from $charset, excluding $skip_chars.
* #param length (integer) length of return value
* #param skip_chars (string) characters to be excluded from $charset
* #param charset (string) characters of posibilities for characters in return val
* #return (string) random string of length $length */
function rand_string(
$length,
$skip_charset = '',
$base_charset='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'){
$skip_len = strlen($skip_charset);
for ($i = 0; $i<$skip_len; $i++){
$base_charset = str_replace($skip_charset[$i], '', $base_charset);
}
cvar_dump($base_charset, '$base_charset after replace');
$str = '';
$count = strlen($base_charset);
while ($length--) {
$str .= $base_charset[mt_rand(0, $count - 1)];
}
return $str;
}
Here are some usage examples. The first two examples use the default value for $base_charset. The last example explicitly defines $base_charset.
echo rand_string(15, 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz');
// 470620078953298
echo rand_string(8, 'abcdefghijklmnopqrstuvwxyz0123456789');
// UKLIHOTFSUZMFPU
echo rand_string(15, 'def', 'abcdef');
// cbcbbccbabccaba
well, I was looking for a solution, and I kindda used #Chad Birch's solution merged with #Gumbo's one. This is what I came up with:
function get_random_string($length, $valid_chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz123456790!·$%&/()=?¿¡',.-;:+*`+´ç")
{
$random_string = "";
$num_valid_chars = strlen($valid_chars);
for ($i = 0; $i < $length; $i++, $random_string .= $valid_chars[mt_rand(1, $num_valid_chars)-1]);
return $random_string;
}
I think comments are pretty much unnecesary since the answers I used to build up this one are already thoroughly commented. Cheers!
If you're not concerned about time, memory, or cpu efficiency, and if your system can handle it, why not give this algorithm a try?!
function randStr($len, $charset = 'abcdABCD0123') {
$out = '';
$str = array();
for ($i = 0; $i < PHP_INT_MAX; $i++) {
$str[$i] = $charset;
shuffle($str);
$charset .= implode($charset, $str);
$charset = str_shuffle($charset);
}
$str = array_flip($str);
$str = array_keys($str);
for ($i = 0; $i < PHP_INT_MAX; $i++) {
shuffle($str);
}
$str = implode('', $str);
for ($i = 0; $i < strlen($str); $i++) {
$index = mt_rand(1, strlen($str));
$out .= $str[$index - 1];
}
for ($i = 0; $i < PHP_INT_MAX; $i++) {
$out = str_shuffle($out);
}
return substr($out, 0, $len);
}
Maybe this will read better if it uses recursion, but I'm not sure if PHP uses tail recursion or not...