Randomly pick element in array then remove from the array

Question

I have an array of phrases. I'd like to randomly pick phrases from the array in a loop. I don't want to pick the same phrase more then once in the loop. I thought I could randomly pick the phrase and then delete it before the next loop.

http://codepad.org/11l0nStX

<?php
for ($i=0; $i<16; $i++) {
    $phrases = array(
        'Hello Sailor', 'Acid Test', 'Bear Garden', 'Botch A Job',
        'Dark Horse', 'In The Red', 'Man Up', 'Pan Out',
        'Quid Pro Quo', 'Rub It In', 'Turncoat', 'Yes Man',
        'All Wet', 'Bag Lady', 'Bean Feast', 'Big Wig',
    );

    $ran_Num = array_rand($phrases);
    $ran_Phrase = $phrases[$ran_Num];
    unset($phrases[$ran_Phrase]);
    echo $ran_Phrase . "\r\n";
    echo count($phrases) . "\r\n";
}

Is it possible to randomly pick a different phrase from the array on each loop?

Use something like array_pop which pops and returns the last value of the array, shortening the array by one element. — andrew-caulfield
– andrew-caulfield, Commented Jun 14, 2013 at 14:27
- The actual error in the above code is due to the array being contained within the loop. Each iteration it gets reset. I haven't tested it but that was plainly obvious. — ArtisticPhoenix
– ArtisticPhoenix, Commented Jun 20, 2022 at 16:23

Mārtiņš Briedis · Accepted Answer · 2013-06-14 14:26:14Z

47

Shuffle the array in random order, and just pop the last element off.

$array = [...];

shuffle($array);

while($element = array_pop($array)){
  echo 'Random element:' . $element;
}

answered Jun 14, 2013 at 14:26

Mārtiņš Briedis

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1 Comment

Vladimir Hraban Over a year ago

I like this approach, simple and clean. The only problem though is that you end up with a shuffled array, so this does not cover all use cases

Toto · Accepted Answer · 2013-06-14 14:44:37Z

4

You could also use array_slice

$ran_Num = array_rand($phrases);
$ran_Phrase = array_slice($phrases, $ran_Num, 1);

answered Jun 14, 2013 at 14:44

Toto

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4 Comments

UnixAgain Over a year ago

How can you assure that the one you removed is the one picked

Toto Over a year ago

From the doc: "Returns the slice."

UnixAgain Over a year ago

Sorry I missed the point. array_rand() returns the index of an indexed array instead of the value at the index.

winkbrace Over a year ago

This is the better solution imho. Note that this returns an array, so you want the first element of that array.

Orangepill · Accepted Answer · 2013-06-14 14:35:57Z

1

You could also use array_rand and array_splice

$array = array('Hello Sailor','Acid Test','Bear Garden','Botch A Job','Dark Horse',
                'In The Red','Man Up','Pan Out','Quid Pro Quo','Rub It In','Turncoat',
                'Yes Man','All Wet','Bag Lady','Bean Feast','Big Wig');

$el = array_rand($array);
$dat = $array[$el];
array_splice($array, $el, 1 );

answered Jun 14, 2013 at 14:35

Orangepill

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Comments

Jawido Kakarot · Accepted Answer · 2021-12-02 09:46:31Z

1

Kinda old question but an easy solution would be to just get random key of the array and then unset it.

  <?php
    $phrases = array('Hello Sailor','Acid Test','Bear Garden','Botch A Job','Dark Horse',
    'In The Red','Man Up','Pan Out','Quid Pro Quo','Rub It In','Turncoat',
    'Yes Man','All Wet','Bag Lady','Bean Feast','Big Wig');

  $ran_Num = array_rand(array_keys($phrases));
  $ran_Phrase = $phrases[$ran_Num];
  unset($phrases[$ran_Phrase]);
  echo $ran_Phrase . "\r\n";
  echo count($phrases) . "\r\n";

answered Dec 2, 2021 at 9:46

Jawido Kakarot

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Comments

terite · Accepted Answer · 2013-06-14 14:38:06Z

The other answers here work, but I want to address your code.

<?php

I pulled the definition of $phrases outside of the loop. By setting it inside the loop, it was being reset every time and that's no good.

$phrases = array('Hello Sailor','Acid Test','Bear Garden','Botch A Job','Dark Horse',
        'In The Red','Man Up','Pan Out','Quid Pro Quo','Rub It In','Turncoat',
         'Yes Man','All Wet','Bag Lady','Bean Feast','Big Wig');

I don't like counting, so I let the computer do it.

for($i=0,$n=count($phrases); $i<$n; $i++){

    $ran_Num = array_rand($phrases);
    $ran_Phrase = $phrases[$ran_Num];

When you unset on an array, the value that goes inside the square brackets should be the index of the array element you want to remove, not the value element itself. The variable inside the brackets has been changed from $ran_Phrase to ran_Num

    unset($phrases[$ran_Num]);
    echo $ran_Phrase."\r\n";
    echo count($phrases)."\r\n";
}
?>

Get Off My Lawn · Accepted Answer · 2013-06-14 14:39:47Z

0

Place the selected values an a new array then check if it exists in the new array if not add it.

<?php
$phrases = array('Hello Sailor','Acid Test','Bear Garden','Botch A Job','Dark Horse',
    'In The Red','Man Up','Pan Out','Quid Pro Quo','Rub It In','Turncoat',
    'Yes Man','All Wet','Bag Lady','Bean Feast','Big Wig');

$default = 16;
if($default > ($c = count($phrases))) $default = $c;

$keys = array_rand($phrases, $default);

$newPhrases = array();
foreach($keys as $key){
    if(!isset($newPhrases[$key])){
        $newPhrases[$key] = $phrases[$key];
    }
}
print_r($newPhrases);

edited Jun 14, 2013 at 14:39

answered Jun 14, 2013 at 14:27

Get Off My Lawn

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3 Comments

Mārtiņš Briedis Over a year ago

in_array and array_rand in a loop would be a bad idea.

Get Off My Lawn Over a year ago

I like you're way better. But this is an option.

Mārtiņš Briedis Over a year ago

You could imprivise - use array_flip once at the start and then search like this: if(isset($phrases[$phrase])). It would be much faster, especially in a loop :)

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