Generating Random String Using PHP - GeeksforGeeks

31 Jul, 2021
Generate a random, unique, alpha-numeric string using PHP.
Examples:
EA070
aBX32gTf

APPROACH 1: Brute ForceThe first approach is the simplest one to understand and thus brute force.It can be achieved as follows:
Store all the possible letters into a string.
Generate random index from 0 to string length-1.
Print the letter at that index.
Perform this step n times (where n is the length of string required).
Program:
<?php$n=10;function getName($n) {    $characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';    $randomString = '';      for ($i = 0; $i < $n; $i++) {        $index = rand(0, strlen($characters) - 1);        $randomString .= $characters[$index];    }      return $randomString;}  echo getName($n);?>
Output 1:
3HDrSOvRIs

Output 2:
lipHh

APPROACH 2: Using Hashing FunctionsPHP has a few functions like md5(), sha1() and hash(), that can be used to hash a string based on certain algorithms like “sha1”, “sha256”, “md5” etc. All these function takes a string as an argument and output an Alpha-Numeric hashed string.
To learn more about these functions click here.
Once we understand how we utilize these functions, our task becomes pretty simple.
Generate a random number using rand() function.
Hash it using one of the above functions.
Program 1:
<?php$str=rand();$result = md5($str);echo $result;?>
Output 1:
2e437510c181dd2ae100fc1661a445d4

Output 2:
256394010059991a71ea05e5d859d2be

Program 2:
<?php$str=rand();$result = sha1($str);echo $result;?>
Output 1:
6eadd9b2c4389d9b109b3b869f66aab5d8f9420a

Output 2:
ca2d3c0993ab87e842d0a7a01f319aca6c587a87

Program 3:
<?php$str = rand();$result = hash("sha256", $str);echo $result;?>
Output 1:
2a41cbc8cc11f8c8d0eb54210fe524748b4def1c5b04fcf18c2d5972e24d11c2

Output 2:
291144c1cbba4de0bf199d37ee265ac95cc2e44e80fd2642b22a6e8ef2f42a39

NOTE: All the above functions are hashing functions, hence the length of the string generated will always depend on the algorithm used, but for an algorithm it will always remain constant. So if you want to generate string of a fixed length, you can either truncate the generated string or concatenate with another string, based on the requirement.
Approach 3:Using uniqid() function.The uniqid( ) function in PHP is an inbuilt function which is used to generate a unique ID based on the current time in microseconds (micro time). By default, it returns a 13 character long unique string.
Program:
<?php $result = uniqid();  echo $result;?> 
Output1:
5bdd0b74e9a6c 

Output2:
5bdd0bbc200c4   

NOTE: All the above approaches are built on rand() and uniqid() functions. These functions are not cryptographically secure random generators. So it is advised that if the degree of randomness affect the security of an application, these methods should be avoided.
Approach 4: Using random_bytes() function. (Cryptographically Secure)The random_bytes() function generates cryptographically secure pseudo-random bytes, which can later be converted to hexadecimal format using bin2hex() function.
Program:
<?php $n = 20;$result = bin2hex(random_bytes($n));echo $result;?> 
Output1:
235aed08a01468f90fa726bd56319fb893967da8 

Output2:
508b84494cdf31bec01566d12a924c75d4baed39 

PHP is a server-side scripting language designed specifically for web development. You can learn PHP from the ground up by following this PHP Tutorial and PHP Examples.
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