How to generate random string in PHP?

By Ujwal Kumar Sahoo

In this article, we will cover how to generate random string in PHP and it’s application in various fields.

Create random strings for a fixed length

In this section, we will discuss the generation of the random string for a fixed length. There are two ways to achieve that:

  • Using a predefined function
  • Using a user-defined function

let us take an example of a pre-defined function for generating strings,

<?php
$str = 'abcdefgh';//range for string generation
$shufflestr = str_shuffle($str);//used to shuffle the range of strings
echo $shufflestr;
?>

Output:

bdaeghfc

Note:-

  • The limitation of the above-predefined function is that you cannot specify more character sets than the given length.

So, to overcome this, we need a user-defined function. Let us take an example of a user-defined  function:

<?php 

function RandomString($num) 
{ 
  // Variable that store final string 
  $final_string = ""; 
  
  //Range of values used for generating string
  $range = "_!@#$^~abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890"; 
  
  // Find the length of created string 
  $length = strlen($range); 
  
  // Loop to create random string 
  for ($i = 0; $i < $num; $i++) 
  { 
    // Generate a random index to pick 
    // characters 
    $index = rand(0, $length - 1); 
    
    // Concatenating the character 
    // in resultant string 
    $final_string.=$range[$index]; 
  } 
  
  // Return the random generated string 
  return $final_string; 
} 

//Creating call to test above function 
$num = 5; 
echo "Random String of length " . $num
. " = " . RandomString($num); 
?>

Output:-

Random String of length 5 = m!@wC

Note:-

For variable length string, just take input through an HTML page and pass it to the PHP page.

Real world application of Random String

There are several examples, but I am taking one of the examples of password generation for a login page. Let us assume some rules for that-

  • The string should be of 8 characters long.
  • The first letter should be capital.
  • It must contain one special character(!@#$^*~).
  • It must contain at least one number.
  • It must contain at least one letter.

Let us make simple coding for that,

<?php
$random_string="";
$arr="!@#$^&*~";//set of special character allowed
$temp=rand(2,8);
//string must be atleast 8 character long
for ($i = 1; $i <=8; $i++){
  if($i==1)
    $random_string = $random_string.chr(rand(65,90));//first letter should be capital
  else{
    if($i==$temp)
        $random_string = $random_string.$arr[rand(0,strlen($arr)-1)];//string contains at least one special character 
    else{
      $temp2=rand(0,1);
      if($temp2==0)
      $random_string = $random_string.chr(rand(97,122));//rest are maybe alphabet
      else
      $random_string = $random_string.chr(rand(48,57));//rest are maybe digit
    }
  }
}
echo $random_string;
?>

Output:-

P$cdra6z

In this way, we can generate strings in a random manner in PHP. If you have any doubt, leave us a comment.

See also,

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