random string

How to generate a random string in PHP

This post has been viewed 75 times.

In this tutorial, we would be dealing with str_repeat, str_shuffle, and substr to generate a random string in PHP.


  • Basic PHP string functions knowledge.

Step 1: Declare the string where you will get your generated random string.



I declared the numbers 0-9 twice to compensate for having both upper and lowercase of letters. We don’t want our generated strings to be filled with letters right?

This function will simply return abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHILJKLMNOPQRSTUVWXYZ0123456789 on the screen which is composed of 73 characters.

Step 2: Use str_repeat to duplicate your initially declared string.

For this example, we used $myString as our declared string.



This function will now return 10 times the length of the returned value from Step 1 which is composed of 730 characters.

Step 3: Use str_shuffle to randomize the position of every character present in $myString.



The purpose of using str_repeat is to add repetitions among the characters. str_repeat together with str_shuffle to have 2 or more of the same characters in a string.

An example is having “aaa” or “abcddd”. If I didn’t use the str_repeat we can only generate a unique set of characters such as “jkl” but never “jjl”.

This function will return a shuffled version of the output in Step 2 and still composed of 730 characters.

Step 4: Use substr to print only the first n characters of the string where n is your desired number of random characters to be generated.

In this example, we would be generating 10 random characters.



This function will return a 10 characters random string. In Step 2, we generated a shuffled version of the 730 characters, but we don’t want to have it long like that right? So we used substr to limit the length of our output.

You can now copy this function as a working code, but if you wish to have an additional feature such as no duplicates, then proceed to Step 5.

Step 5: Use recursion to check for duplicates. This will not allow our function to return a duplicated string.


This function will have the same output as we have in Step 4 but the upside of this function is that it will not return a duplicated string. Instead, the output will only be generated once and never again but you need the right condition for it to work.

Basic usage:

That’s it. We have created a random character generator using PHP.

Hello, I am a freelance website and mobile application developer. I am also the owner of this website, so if you have any projects for me you can contact me at [email protected] or use the contact page. When I’m not doing some work, I can be found watching Anime/Asian Dramas/American TV Series, playing computer games, and writing tutorials on this website. I run the program repeatedly hoping the error won’t show up next time.