Selecting a random element from a PHP associative array

Question

I've got an associative array in PHP and want to select a random key/value pair out of it. Here's what I have so far:

Initialize.

$locations = array();

Loops through a SQL query and adds key/val pairs:

array_push($locations, "'$location_id' => '$location_name'");

Later on, I select a random index of the array:

$rand = array_rand($locations);

Rand is just a number. So locations[$rand] gives me something like:

'1' => 'Location 1'

OK great, an assoc array element. At this point, I do not know the key of this assoc array, so I've tried the following things:

foreach($locations[$rand] as $loc_id => $location_name) { 
    echo "$key : $value<br/>\n";
}

$loc_id, $location_name = each($locations[$rand]);

$location_name = $locations[key($rand)];

None of these 3 attempts work. They all throw errors like "Passed variable is not an array".

I'm sure there's some simple 1 liner that can pluck a random key/value pair from the array. Or my syntax is off. I'd really appreciate the help.

Phill Healey · Accepted Answer · 2024-03-12 12:09:57Z

43

$array = array('a' => 1, 'b' => 2);
$key = array_rand($array);
$value = $array[$key];

Your problem is in array_push($locations, "'$location_id' => '$location_name'");. Do this instead: $locations[$location_id] = $location_name;. Then array_rand($location) will return a random $location_id; and you can get the name with $name = $locations[$location_id].

edited Mar 12, 2024 at 12:09

Phill Healey

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answered Aug 26, 2011 at 18:40

Arnaud Le Blanc

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2 Comments

Arnaud Le Blanc Over a year ago

Your problem is in array_push($locations, "'$location_id' => '$location_name'");. Do this instead: $locations[$location_id] = $location_name;. Then array_rand($location) will return a random $location_id; and you can get the name with $name = $locations[$location_id].

Jeff Over a year ago

you're all correct, of course - i just picked this one bc i work best with example code. and yeah, i'm pretty embarrassed about the push not being correct. i code a ton in perl (w hashes) so i should have known better! THANK YOU!

Paul · Accepted Answer · 2011-08-26 18:51:47Z

6

array_rand() returns a key from the array, not a value. You can just use:

$location_name = $locations[$rand];

To get the location name.

Here's a full example: http://codepad.org/zR2YdMGN

Just click submit a few times, you'll see the random working.

edited Aug 26, 2011 at 18:51

answered Aug 26, 2011 at 18:39

Paul

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3 Comments

Mark Biesheuvel Over a year ago

This still doesn't give the key.

Mark Biesheuvel Over a year ago

Ok, sorry. Then the claim ($rand is just a number) from the OP is wrong. And I was foolish enough to not verify this claim.

Paul Over a year ago

@M_rk It returns the key :) I updated my answer so that it has a link to the PHP Man page for array_rand

leealex · Accepted Answer · 2022-08-30 09:37:53Z

1

You can do it with one line:


$randomValue = array_rand(array_flip(['value_1', 'value_2']))

You will get the value right away instead of the key.

answered Aug 30, 2022 at 9:37

leealex

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