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Dealing with sparse arrays

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This snippet assumes you want to walk the numbered array items only, as you would with a normal for loop, but a for loop up to count($array) won't work with a sparse array because the highest array index will always be higher than the array count.

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  1. // a sparse array has non consecutive integers for the indexes,
  2. $array = array(7=>'foo', 19=>'bar';
  3. $array[] = 'baz';
  4.  
  5. // note that count($array) will return 3 here, not much use
  6. foreach($array as $i => $el) {
  7.     if(is_int($i)) { // in case this array has mixed keys
  8.         echo $el;
  9.     }
  10. }
  11.  
  12. // if you want to de-sparse the array before you walk it, do this
  13. function array_desparse(&$array, $filler=NULL) {
  14. 	$max = -1;
  15. 	for (end($array); $key = key($array); prev($array)) {
  16. 		if (is_int($key) and $key > $max) {
  17. 			$max = $key;
  18. 		}
  19. 	}
  20. 	for ($i = 0; $i <= $max; $i++) {
  21. 		if (!array_key_exists($i, $array)) {
  22. 			$array[$i] = $filler;
  23. 		}
  24. 	}
  25. 	ksort($array);
  26. }

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