PHP return randomised array

Question

I am trying to create a new array from an existing one with a random number of records between 2 and 10, I have this so far

//Select a random number
$random_number = (rand(2,10));

// Setup an array of names
$names = array("john", "joe", "simon", "peter", "paul");

// Create new array
$random_field_names = array_rand($names, $random_number);

print_r($random_field_names);

This gives me an array that looks like this

Array
(
    [0] => 0
    [1] => 10
    [2] => 11
)

Where am I going wrong?

Can you add an example of what you want the desired output to be? I'm a little confused about what you are trying to do. — kunruh
– kunruh, Commented Nov 24, 2016 at 21:26

LdiCO · Accepted Answer · 2016-11-24 21:30:20Z

2

Use the key to get the value you want :

//Select a random number
$random_number = (rand(2,10));

// Setup an array of names
$names = array("john", "joe", "simon", "peter", "paul");

// Create new array
$random_field_names = array_rand($names, $random_number);

print_r($names[$random_field_names]);

answered Nov 24, 2016 at 21:30

LdiCO

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Comments

trincot · Accepted Answer · 2016-11-24 22:18:03Z

1

The description of array_rand explains why you don't get the names (I stress in bold):

Picks one or more random entries out of an array, and returns the key (or keys) of the random entries.

You seem to want the values. That you can achieve like this:

 array_intersect_key($names,  array_flip(array_rand($names, $random_number)));

Also make sure your random number is not greater than the array size:

$random_number = rand(2,5);
$names = array("john", "joe", "simon", "peter", "paul");
$result = array_intersect_key($names,  array_flip(array_rand($names, $random_number)));
print_r ($result);

Note that the result maintains the original keys. If you want to renumber the keys to get an indexed array starting with index 0, then apply array_values to the result:

$result = array_values(array_intersect_key($names,  array_flip(array_rand($names, $random_number))));

edited Nov 24, 2016 at 22:18

answered Nov 24, 2016 at 21:31

trincot

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3 Comments

fightstarr20 Over a year ago

When I try and extract an item from the new array using $result[1] I get no results, is this something to do with the way the new array is constructed?

trincot Over a year ago

Indeed, the result array maintains the original keys. See addition to my answer.

fightstarr20 Over a year ago

Thank you very much, makes much more sense now

Shira · Accepted Answer · 2016-11-24 21:28:20Z

1

syntax error on line 5 - missing quote after "simon
array_rand() returns random key(s), not values
rand(2,10) won't work in all cases as there are only 5 entries in the array; from PHP docs: Trying to pick more elements than there are in the array will result in an E_WARNING level error, and NULL will be returned.

If you want to randomize the entire array, use shuffle().

answered Nov 24, 2016 at 21:28

Shira

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