Hi i need to save a 010 number in $number and if i do like this php will remove the starting 0
$number = 010
And echo of this will return 10 how can i make it not to remove the initial 0
BR
Martin
Use it as a String:
$number = '010';
Use str_pad() function.
echo str_pad('10',3,'0',STR_PAD_LEFT)
http://php.net/manual/en/function.str-pad.php
Do remember that numbers starting with 0 can also be treated as octal number notation by the PHP compiler, hence if you want to work with decimal numbers, simply use:
$num = '010';
This way the number is saved, can be stored in the database and manipulated like any other number. (Thx to the fact that PHP is very loosely typed language.)
Another method to use would be:
Save number as $num = 10;
Later while printing the value you can use sprintf, like:
sprintf("%03d", $i);
This will print your number in 3 digit format, hence 0 will be added automatically.
Another method:
<?php
$num = 10;
$zerofill = 3;
echo str_pad($num, $zerofill, "0", STR_PAD_LEFT);
/* Returns the wanted result of '010' */
?>
You can have a look at the various options available to you and make a decision. Each of the method given above will give you a correct output.
I'm building a simple URL shortening script, I want to hash the URL to serve as a unique id but if I used something like MD5 the URL wouldn't be very short.
Is their some hashing functions or anyway to create a unique ID thats only 4 or 5 digits long?
Use auto incrementing integers and convert them into identifiers consisting of all letters (lower & uppercase) to shorten them:
function ShortURL($integer, $chr='abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ') {
// the $chr has all the characters you want to use in the url's;
$base = strlen($chr);
// number of characters = base
$string = '';
do {
// start looping through the integer and getting the remainders using the base
$remainder = $integer % $base;
// replace that remainder with the corresponding the $chr using the index
$string .= $chr[$remainder];
// reduce the integer with the remainder and divide the sum with the base
$integer = ($integer - $remainder) / $base;
} while($integer > 0);
// continue doing that until integer reaches 0;
return $string;
}
and the corresponding function to get them back to integers:
function LongURL($string, $chr='abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ') {
// this is just reversing everything that was done in the other function, one important thing to note is to use the same $chr as you did in the ShortURL
$array = array_flip(str_split($chr));
$base = strlen($chr);
$integer = 0;
$length = strlen($string);
for($c = 0; $c < $length; ++$c) {
$integer += $array[$string[$c]] * pow($base, $length - $c - 1);
}
return $integer;
}
Hashing will cause collisions. Just use an autoincrementing value. This includes using alphanumeric characters too to compress it. That is how most URL shortners work.
niklas's answer below is wonderfully done.
The advantage of using MD5 (or equivalent methods) is that the number of possibilities is so large that you can, for all practical purposes, assume that the value is unique. To ensure that a 4-digit random-like ID is unique would require a database to track existing IDs.
Essentially you have to repeatedly generate IDs and check against the DB.
You could always just keep the first 5 characters of a MD5 and if it already exists you add a random value to the url-string and retry until you get a unique one.
I just copied the code and ran it, and it appears that he string function are backwards. I entered the number generated in the shorturl and ran it back thought and got a different number. So I decoded the number and found the string has to be fed back into long url in reverse with the current coding above.
how can i convert a string(i.e. email address) to unique integers, to use them as an ID.
The amount of information a PHP integer may store is limited. The amount of information you can store in a string is not (at least if the string isn't unreasonably long.)
Thus you would need to compress your arbitrary-length string to an non-arbitrary-length integer. This is impossible without data loss.
You may use a hashing algorithm, but hashing algorithms may always have collisions. Especially if you want to hash a string to an integer the collision probability is pretty high - integers can store only very little data.
Thus you shall either stick with the email or use an auto incrementing integer field.
Try the binhex function
from the above site:
<?php
$str = "Hello world!";
echo bin2hex($str) . "<br />";
echo pack("H*",bin2hex($str)) . "<br />";
?>
outputs
48656c6c6f20776f726c6421
Hello world!
Why not just have an auto-increment ID field on the database?
This code generates 64bit number which can be use as it or as a bigInt / similar data-type for databases like MySQL etc.
function get64BitNumber($str)
{
return gmp_strval(gmp_init(substr(md5($str), 0, 16), 16), 10);
}
echo get64BitNumber('Hello World!'); // 17079728445181560374
echo get64BitNumber('Hello World#'); // 2208921763183434891
echo get64BitNumber('http://waqaralamgir.tk/'); // 12007604953204508983
echo get64BitNumber('12345678910'); // 4841164765122470932
If the emails are ascii text, you could use PHP ord function to generate a unique integer, but it will be a very large number!
The approach would be to work through the email address one character at a time, calling ord for each of them. The ord function returns an integer uniquely expressing the character's value. You can pad each of these numbers with zeros and then use string concatenation to plug them into each other.
Consider "abc".
ord("a");
>> 97
ord("b");
>> 98
ord("c");
>> 99
Pad these numbers with a 0, and you have a unique number for it, that is: 970980990.
I hope that helps!
You can use crc32 function.
Example:
$email = "user#gmail.com";
echo $email . " = " . crc32($email);
Live example: https://repl.it/repls/HonorableRespectfulBundledsoftware
Why not create your own associative table locally that will bind the emails with unique integers?
So the work flow would be in the lines of:
1 get the record from the ldap server.
2 check it locally if it has already an int assigned.
2.1 if yes use that int.
2.2 if no, generate an associative row in the table locally.
3 do your things with the unique ids.
Does that make sense?
You can use this function:
function stringToInteger($string) {
$output = '';
for ($i = 0; $i < strlen($string); $i++) {
$output .= (string) ord($string[$i]);
}
return (int) $output;
}
A bit ugly, but works :)
I need help to change a character in php.
I got some code from the web:
char dest='a';
int conv=(int)dest;
Can I use this code to convert a character into numeric? Or do you have any ideas?
I just want to show the result as a decimal number:
if null == 0
if A == 1
Use ord() to return the ascii value. Subtract 96 to return a number where a=1, b=2....
Upper and lower case letters have different ASCII values, so if you want to handle them the same, you can use strtolower() to convert upper case to lower case.
To handle the NULL case, simply use if($dest). This will be true if $dest is something other than NULL or 0.
PHP is a loosely typed language, so there is no need to declare the types. So char dest='a'; is incorrect. Variables have $ prefix in PHP and no type declaration, so it should be $dest = 'a';.
Live Example
<?php
function toNumber($dest)
{
if ($dest)
return ord(strtolower($dest)) - 96;
else
return 0;
}
// Let's test the function...
echo toNumber(NULL) . " ";
echo toNumber('a') . " ";
echo toNumber('B') . " ";
echo toNumber('c');
// Output is:
// 0 1 2 3
?>
PS:
You can look at the ASCII values here.
It does indeed work as in the sample, except that you should be using php syntax (and as a sidenote: the language that code you found most probably was, it did not do the same thing).
So:
$in = "123";
$out = (int)$in;
Afterwards the following will be true:
$out === 123
This may help you:
http://www.php.net/manual/en/function.ord.php
So, if you need the ASCII code you will need to do:
$dest = 'a';
$conv = ord($dest);
If you want something like:
a == 1
b == 2
.
.
.
you should do:
$dest = 'a';
$conv = ord($dest)-96;
For more info on the ASCII codes: http://www.asciitable.com/
And for the function ord: http://www.php.net/manual/en/function.ord.php
It's very hard to answer because it's not a real question but just a little bit of it.
But if you ask.
It seems you need some translation table, that defines links between letters and numbers
A -> 2
B -> 3
C -> 4
S -> 1
or whatever.
You can achieve this by using an array, where keys would be these letters and values - desired numbers.
$defects_arr = array(
'A' -> 2,
'B' -> 3,
'C' -> 4'
'S' -> 1
};
Thus, you can convert these letters to numbers
$letter = 'A';
$number = $defects_arr($letter);
echo $number; // outputs 1
But it still seems is not what you want.
Do these defect types have any verbose equivalents? If so, why not to use them instead of letters?
Telling the whole story instead of little bit of it will help you to avoid mistakes and will save a ton of time, both yours and those who to answer.
Out of this question, if you are looking for convert RT0005 to 5
$max = 'RT0005';
return base_convert($max,10,10);
// return 5
I want to create a unique id but uniqid() is giving something like '492607b0ee414'. What i would like is something similar to what tinyurl gives: '64k8ra'. The shorter, the better. The only requirements are that it should not have an obvious order and that it should look prettier than a seemingly random sequence of numbers. Letters are preferred over numbers and ideally it would not be mixed case. As the number of entries will not be that many (up to 10000 or so) the risk of collision isn't a huge factor.
Any suggestions appreciated.
Make a small function that returns random letters for a given length:
<?php
function generate_random_letters($length) {
$random = '';
for ($i = 0; $i < $length; $i++) {
$random .= chr(rand(ord('a'), ord('z')));
}
return $random;
}
Then you'll want to call that until it's unique, in pseudo-code depending on where you'd store that information:
do {
$unique = generate_random_letters(6);
} while (is_in_table($unique));
add_to_table($unique);
You might also want to make sure the letters do not form a word in a dictionnary. May it be the whole english dictionnary or just a bad-word dictionnary to avoid things a customer would find of bad-taste.
EDIT: I would also add this only make sense if, as you intend to use it, it's not for a big amount of items because this could get pretty slow the more collisions you get (getting an ID already in the table). Of course, you'll want an indexed table and you'll want to tweak the number of letters in the ID to avoid collision. In this case, with 6 letters, you'd have 26^6 = 308915776 possible unique IDs (minus bad words) which should be enough for your need of 10000.
EDIT:
If you want a combinations of letters and numbers you can use the following code:
$random .= rand(0, 1) ? rand(0, 9) : chr(rand(ord('a'), ord('z')));
#gen_uuid() by gord.
preg_replace got some nasty utf-8 problems, which causes the uid somtimes to contain "+" or "/".
To get around this, you have to explicitly make the pattern utf-8
function gen_uuid($len=8) {
$hex = md5("yourSaltHere" . uniqid("", true));
$pack = pack('H*', $hex);
$tmp = base64_encode($pack);
$uid = preg_replace("#(*UTF8)[^A-Za-z0-9]#", "", $tmp);
$len = max(4, min(128, $len));
while (strlen($uid) < $len)
$uid .= gen_uuid(22);
return substr($uid, 0, $len);
}
Took me quite a while to find that, perhaps it's saves somebody else a headache
You can achieve that with less code:
function gen_uid($l=10){
return substr(str_shuffle("0123456789abcdefghijklmnopqrstuvwxyz"), 0, $l);
}
Result (examples):
cjnp56brdy
9d5uv84zfa
ih162lryez
ri4ocf6tkj
xj04s83egi
There are two ways to obtain a reliably unique ID: Make it so long and variable that the chances of a collision are spectacularly small (as with a GUID) or store all generated IDs in a table for lookup (either in memory or in a DB or a file) to verify uniqueness upon generation.
If you're really asking how you can generate such a short key and guarantee its uniqueness without some kind of duplicate check, the answer is, you can't.
Here's the routine I use for random base62s of any length...
Calling gen_uuid() returns strings like WJX0u0jV, E9EMaZ3P etc.
By default this returns 8 digits, hence a space of 64^8 or roughly 10^14,
this is often enough to make collisions quite rare.
For a larger or smaller string, pass in $len as desired. No limit in length, as I append until satisfied [up to safety limit of 128 chars, which can be removed].
Note, use a random salt inside the md5 [or sha1 if you prefer], so it cant easily be reverse-engineered.
I didn't find any reliable base62 conversions on the web, hence this approach of stripping chars from the base64 result.
Use freely under BSD licence,
enjoy,
gord
function gen_uuid($len=8)
{
$hex = md5("your_random_salt_here_31415" . uniqid("", true));
$pack = pack('H*', $hex);
$uid = base64_encode($pack); // max 22 chars
$uid = ereg_replace("[^A-Za-z0-9]", "", $uid); // mixed case
//$uid = ereg_replace("[^A-Z0-9]", "", strtoupper($uid)); // uppercase only
if ($len<4)
$len=4;
if ($len>128)
$len=128; // prevent silliness, can remove
while (strlen($uid)<$len)
$uid = $uid . gen_uuid(22); // append until length achieved
return substr($uid, 0, $len);
}
Really simple solution:
Make the unique ID with:
$id = 100;
base_convert($id, 10, 36);
Get the original value again:
intval($str,36);
Can't take credit for this as it's from another stack overflow page, but I thought the solution was so elegant and awesome that it was worth copying over to this thread for people referencing this.
You could use the Id and just convert it to base-36 number if you want to convert it back and forth. Can be used for any table with an integer id.
function toUId($baseId, $multiplier = 1) {
return base_convert($baseId * $multiplier, 10, 36);
}
function fromUId($uid, $multiplier = 1) {
return (int) base_convert($uid, 36, 10) / $multiplier;
}
echo toUId(10000, 11111);
1u5h0w
echo fromUId('1u5h0w', 11111);
10000
Smart people can probably figure it out with enough id examples. Dont let this obscurity replace security.
I came up with what I think is a pretty cool solution doing this without a uniqueness check. I thought I'd share for any future visitors.
A counter is a really easy way to guarantee uniqueness or if you're using a database a primary key also guarantees uniqueness. The problem is it looks bad and and might be vulnerable. So I took the sequence and jumbled it up with a cipher. Since the cipher can be reversed, I know each id is unique while still appearing random.
It's python not php, but I uploaded the code here:
https://github.com/adecker89/Tiny-Unique-Identifiers
Letters are pretty, digits are ugly.
You want random strings, but don't want "ugly" random strings?
Create a random number and print it in alpha-style (base-26), like the reservation "numbers" that airlines give.
There's no general-purpose base conversion functions built into PHP, as far as I know, so you'd need to code that bit yourself.
Another alternative: use uniqid() and get rid of the digits.
function strip_digits_from_string($string) {
return preg_replace('/[0-9]/', '', $string);
}
Or replace them with letters:
function replace_digits_with_letters($string) {
return strtr($string, '0123456789', 'abcdefghij');
}
You can also do it like tihs:
public static function generateCode($length = 6)
{
$az = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
$azr = rand(0, 51);
$azs = substr($az, $azr, 10);
$stamp = hash('sha256', time());
$mt = hash('sha256', mt_rand(5, 20));
$alpha = hash('sha256', $azs);
$hash = str_shuffle($stamp . $mt . $alpha);
$code = ucfirst(substr($hash, $azr, $length));
return $code;
}
You can do that without unclean/costy stuff like loops, String concatenations or multiple calls to rand(), in a clean and easy to read way. Also, it is better to use mt_rand():
function createRandomString($length)
{
$random = mt_rand(0, (1 << ($length << 2)) - 1);
return dechex($random);
}
If you need the String to have the exact length in any case, just pad the hex number with zeros:
function createRandomString($length)
{
$random = mt_rand(0, (1 << ($length << 2)) - 1);
$number = dechex($random);
return str_pad($number, $length, '0', STR_PAD_LEFT);
}
The "theoretical backdraw" is, that you are limited to PHPs capabilities - but this is more a philosophical issue in that case ;) Let's go through it anyways:
PHP is limited in what it can represent as a hex number doing it like this. This would be $length <= 8 at least on a 32bit system, where PHPs limitation for this should be 4.294.967.295 .
PHPs random number generator also has a maximum. For mt_rand() at least on a 32bit system, it should be 2.147.483.647
So you are theoretically limited to 2.147.483.647 IDs.
Coming back to the topic - the intuitive do { (generate ID) } while { (id is not uniqe) } (insert id) has one drawback and one possible flaw that might drive you straight to darkness...
Drawback: The validation is pessimistic. Doing it like this always requires a check at the database. Having enough keyspace (for example length of 5 for your 10k entries) will quite unlikely cause collisions as often, as it might be comparably less resource consuming to just try to store the data and retry only in case of a UNIQUE KEY error.
Flaw: User A retrieves an ID that gets verified as not taken yet. Then the code will try to insert the data. But in the meantime, User B entered the same loop and unfortunately retrieves the same random number, because User A is not stored yet and this ID was still free. Now the system stores either User B or User A, and when attempting to store the second User, there already is the other one in the meantime - having the same ID.
You would need to handle that exception in any case and need to re-try the insertion with a newly created ID. Adding this whilst keeping the pessimistic checking loop (that you would need to re-enter) will result in quite ugly and hard to follow code. Fortunately the solution to this is the same like the one to the drawback: Just go for it in the first place and try to store the data. In case of a UNIQUE KEY error just retry with a new ID.
Take a lookt at this article
Create short IDs with PHP - Like Youtube or TinyURL
It explains how to generate short unique ids from your bdd ids, like youtube does.
Actually, the function in the article is very related to php function base_convert which converts a number from a base to another (but is only up to base 36).
10 chars:
substr(uniqid(),-10);
5 binary chars:
hex2bin( substr(uniqid(),-10) );
8 base64 chars:
base64_encode( hex2bin( substr(uniqid(),-10) ) );
function rand_str($len = 12, $type = '111', $add = null) {
$rand = ($type[0] == '1' ? 'abcdefghijklmnpqrstuvwxyz' : '') .
($type[1] == '1' ? 'ABCDEFGHIJKLMNPQRSTUVWXYZ' : '') .
($type[2] == '1' ? '123456789' : '') .
(strlen($add) > 0 ? $add : '');
if(empty($rand)) $rand = sha1( uniqid(mt_rand(), true) . uniqid( uniqid(mt_rand(), true), true) );
return substr(str_shuffle( str_repeat($rand, 2) ), 0, $len);
}
If you do like a longer version of unique Id use this:
$uniqueid = sha1(md5(time()));
Best Answer Yet: Smallest Unique "Hash Like" String Given Unique Database ID - PHP Solution, No Third Party Libraries Required.
Here's the code:
<?php
/*
THE FOLLOWING CODE WILL PRINT:
A database_id value of 200 maps to 5K
A database_id value of 1 maps to 1
A database_id value of 1987645 maps to 16LOD
*/
$database_id = 200;
$base36value = dec2string($database_id, 36);
echo "A database_id value of 200 maps to $base36value\n";
$database_id = 1;
$base36value = dec2string($database_id, 36);
echo "A database_id value of 1 maps to $base36value\n";
$database_id = 1987645;
$base36value = dec2string($database_id, 36);
echo "A database_id value of 1987645 maps to $base36value\n";
// HERE'S THE FUNCTION THAT DOES THE HEAVY LIFTING...
function dec2string ($decimal, $base)
// convert a decimal number into a string using $base
{
//DebugBreak();
global $error;
$string = null;
$base = (int)$base;
if ($base < 2 | $base > 36 | $base == 10) {
echo 'BASE must be in the range 2-9 or 11-36';
exit;
} // if
// maximum character string is 36 characters
$charset = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';
// strip off excess characters (anything beyond $base)
$charset = substr($charset, 0, $base);
if (!ereg('(^[0-9]{1,50}$)', trim($decimal))) {
$error['dec_input'] = 'Value must be a positive integer with < 50 digits';
return false;
} // if
do {
// get remainder after dividing by BASE
$remainder = bcmod($decimal, $base);
$char = substr($charset, $remainder, 1); // get CHAR from array
$string = "$char$string"; // prepend to output
//$decimal = ($decimal - $remainder) / $base;
$decimal = bcdiv(bcsub($decimal, $remainder), $base);
} while ($decimal > 0);
return $string;
}
?>