PHP: Best way to iterate two parallel arrays?

As seen in this other answer, there are several ways to iterate two same-sized arrays simultaneously; however, all of the methods have a rather significant pitfall. Here are some of the caveats with the methods suggested:

  • You can't use FALSE values in one of the arrays.
  • You can only use scalar values in one of the arrays.
  • You must use numerically indexed arrays.
  • Both arrays must share the same keys.
  • Etc.

My question is - is there a method for doing this which doesn't suffer from any of these (or other) significant caveats?

Bear in mind that I'm simply asking this out of curiosity; I have no use-case in mind, nor do I even know if such a case actually exists or would be useful/practical in a real-world scenario. However, here is some example data:

$arr1 = [ 'a' => 1, 'b' => FALSE, 'c' => new DateTime() ];
$arr2 = [ 'foo', TRUE, 7 ];

Answers


You can use a MultipleIterator:

$iterator = new MultipleIterator;
$iterator->attachIterator(new ArrayIterator($array1));
$iterator->attachIterator(new ArrayIterator($array2));

foreach ($iterator as $values) {
    var_dump($values[0], $values[1]);
}

You can find more examples concerning the various options in the docs.


As of PHP 5.5 you can do this:

foreach (array_map(null, $array1, $array2) as list($item1, $item2))
{
    var_dump($item1);
    var_dump($item2);
}

http://us3.php.net/manual/en/control-structures.foreach.php#control-structures.foreach.list


<?php

$arr1 = array( 'a' => 1, 'b' => FALSE, 'c' => new DateTime() );
$arr2 = array( 'foo', TRUE, 7, 5 );


reset($arr1);
reset($arr2);    

while ( (list($key, $val) = each($arr1))
    && (list($key2, $val2) = each($arr2))
) {
    var_dump($val,$val2);
    // or whatever you wanted to do with them
}

http://www.php.net/manual/en/function.each.php


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