PHP srand( ) Function

Many times while designing questions or algorithms we require to generate random numbers. We already have studied a built-in function in PHP for generating random numbers in the article PHP |rand() Function. The rand() function is used to generate random numbers. If we generate a sequence of random numbers with rand() function, it will create the same sequence, again and again, every time the program runs. To solve this issue another built-in function of PHP, srand() can be used.

The srand() function in PHP is used to seed the random number generator rand(). The srand() function sets the starting point for producing a series of pseudo-random integers. If srand() is not called, the rand() seed is set as if srand(1) were called at program start. The srand() function seeds the random number generator with seed(arg) or with a random value if no seed(arg) is given.

Syntax:

srand($seed)

Parameters: This function accepts a single parameter seed. It is an optional parameter and is of integer type. It specifies the seed value.

Return Value: This function does not returns any value.

Examples:

Input : srand(time());
Output : 1793542495

Input : srand(5)
Output : 3

Below programs illustrate the srand() function in PHP:

1. When timestamp is used as the $seed value along with srand() function:

   
   

   
   
   

   <?php    srand(time());    echo(rand());    ?>

   Output:

   1793542495

2. When a user-defined seed value is passed as an argument with srand() function:

   
   

   
   
   

   <?php    srand(5);     echo(rand(1, 10));     ?>

   Output:

   3

Important Points To Note:

• srand() function can be used to generate random numbers.
• srand() function doesn\’t create the same sequence of random numbers like the rand() function.
• It doesn’t have a return value.

References:
http://php.net/manual/en/function.srand.php