PHP - Sequence through array and repeat [modulo-operator]

Question

I need to be able to loop an array of items and give them a value from another array and I cant quite get my head around it.

My Array

$myarray = array('a','b','c');

Lets say I have a foreach loop and I loop through 6 items in total.

How do I get the following output

item1 = a
item2 = b
item3 = c
item4 = a
item5 = b
item6 = c

My code looks something like this.

$myarray = array('a','b','c'); 
$items = array(0,1,2,3,4,5,6);
foreach ($items as $item) {
   echo $myarray[$item];
}

Online example. http://codepad.viper-7.com/V6P238

I want to of course be able to loop through an infinite amount of times

use a foreach loop nested in a for loop, run the for loop for as long as you want it to run — Troy Cosentino
– Troy Cosentino, Commented Aug 1, 2012 at 17:33
ive tried a for loop and i obviously get stuck every I reach item 4, as there is no corresponding key/value in $myarray — Blowsie
– Blowsie, Commented Aug 1, 2012 at 17:37

KingCrunch · Accepted Answer · 2012-08-01 17:40:48Z

6

$myarray = array('a','b','c'); 
$count = count($myarray);
foreach ($array as $index => $value) {
  echo $value . ' = ' . $myarray[$index % $count] . "\n";
}

% is the modulo-operator. It returns

Remainder of $a divided by $b.

what means

0 % 3 = 0
1 % 3 = 1
2 % 3 = 2
3 % 3 = 0
4 % 3 = 1

and so on. In our case this reflects the indices of the array $myarray, that we want to retrieve.

answered Aug 1, 2012 at 17:40

KingCrunch

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8 Comments

Palladium Over a year ago

Why $index % $count if you're only doing one foreach anyway? It's still the same as $index.

KingCrunch Over a year ago

@Palladium No, it isn't. $index is the index of the current $value, whereas $count is a static value.

Palladium Over a year ago

Yes it is. $index, being defined as the numeric keys of the elements, will never be higher than $count (given his test array). Your cases of 3%3 and 4%3 will never happen in your foreach loop.

KingCrunch Over a year ago

@Palladium In his example the OPs speaks from an array with size 6 items in $array (in his edit he called it $items), but $myarray is of size 3, thus it will happen.

KingCrunch Over a year ago

@Palladium The sentence "Lets say I have a foreach loop and I loop through 6 items in total." stands there right from the beginning ....

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Palladium · Accepted Answer · 2012-08-01 17:40:43Z

1

If you want an arbitrary number of loops to be done, you can use the modulus operator to cycle through your keys:

$loop = //how much you want the loop to go
//...
for ($i = 0, $i < $loop, $i++) {
    $key = $i % count($myarray);
    echo $i, ' = ', $myarray[$key];
}

answered Aug 1, 2012 at 17:40

Palladium

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Comments

Gordon Bailey · Accepted Answer · 2012-08-01 17:41:29Z

1

I think what you are looking for is the modulo operator. Try something like this:

for ($i = 1; $i <= $NUMBER_OF_ITEMS; $i++) {
    echo "item$i = ".$myarray[$i % count($myarray)]."\n";
}

answered Aug 1, 2012 at 17:41

Gordon Bailey

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