How to return a number of random strings from a group of strings using PHP?

Question

I have a group of 200 unique strings, and I need a PHP script to return 100 random strings from that group of 200, avoiding repetition - how to do this??

Answer 1

First of all, you need to generate 100 random numbers between 0 and 199 and save them in an array. To avoid repetition, we will use a while() loop:

$rand_numbers = array();

/* This first loop is to get 100 numbers

while($counter<100) {

static $counter = 0;

/* Now we generate the number */

$tempnum = rand(0,199);

/* We use a while() loop to keep generating random numbers UNTIL the number generated is not in the array $rand_numbers */

while(!in_array( $tempnum, $rand_numbers)) {

$tempnum = rand(0,199);

}

/* We add the no repeated number to the array */

$rand_numbers[ $counter ] = $tempnum;

$counter++;

}

Ok, now we get the array of strings using the random numbers of the other array:

for($f = 0;$f<100; $f++) {

echo $strings[ $rand_numbers[ $f ] ];

}

And it is done!!

function in_array() checks for a value in an array: http://www.php.net/in_array

Hope it works.

Answer 2

Have you tried the array_rand function:-

http://uk2.php.net/manual/en/function.ar...

This returns a number of random elements from any array, however the docs don't say whether they are distinct (but I'm guessing they are) - you can run some tests to see if this is the case by creating an array of numbers 0-99 and seeing what the outputs are when run several times.

Answer 3

I concur with MH about using the array_rand function.  

In conjunction with using an associative array, this will solve you query.

(associate arrays must contain a unique key)

e.g.

// here is an example with 5 strings

// if you uncomment the echo statement in the loop and print_r($strings)

// you'll notice that two entries for 'unique string 5'

// are in our data but only 1 entry will exist in $strings.

$uniq_strings="unique string 1\nunique string 2\nunique string 3\nunique string 4\nunique string 5\nunique string 5\nunique string 5";

print_r( return_rand($uniq_strings, 5));

function return_rand($uniq_strings, $num){

    $strings = Array();

    foreach ( split("\n", $uniq_strings) as $str ) {

            //echo $str."\n";

            $strings[$str]++;

    }

    //print_r($strings);

    return( array_rand($strings, $num) );

}

?>

Answer 4

The best way is to put them in an array and then:

$a = array (strings in here);

$b = array (); // result array

for ($i = 0; $i < 200; $i++) {

$r = rand(0,count($a) - 1);

$b[] = $a[$r];

$a = array_splice ($a, $r, 1);

}

That should do the trick.