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Let's say I've got this string:

$str = '1-2-3';

and I explode this like so:

$strSplit = explode('-', $str);

what would be the best way to check if I've got the correct number of elements and whether they are numeric (because the input can vary)?

Straightforward, I would say something like this:

if (isset($strSplit[0]) && is_numeric($strSplit[0]) && isset($strSplit[1]) && is_numeric($strSplit[1]) && isset($strSplit[2]) && is_numeric($strSplit[2]) { // some code }

But you could also do:

if (count($strSplit) === 3 && is_numeric($strSplit[0]) && is_numeric($strSplit[1]) && is_numeric($strSplit[2])) { // some code }

You can use some array functions to check for the is_numeric part, but that seems fussy, less readable and is probably slower. I could be wrong, though...

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2 Answers 2

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There are several options.

My favorite (based on readablity and simplicity) is using array_filter to remove everything that is not a number from the array and then comparing with the original to see if anything changed, then using count to make sure you have the correct number of elements:

$str = '1-foo-3'; $strSplit = explode('-', $str); if(count($strSplit) == 3 && $strSplit == array_filter($strSplit, 'is_numeric')){ // array is numeric // run code } else { // array is non-numeric }

Edit: did some speed testing and tried a few more options and validations.

I speedtested with the following inputs:

A: $strSplit = explode('-', '1-2-3');//3 elements, all numeric //evaluates true B: $strSplit = explode('-', '1-foo-3-4');//4 elements, not all numeric //evaluates false

The results (after 1 million cycles) were as follows :

Static isset and is_numeric :

if (isset($strSplit[0]) && is_numeric($strSplit[0]) && isset($strSplit[1]) && is_numeric($strSplit[1]) && isset($strSplit[2]) && is_numeric($strSplit[2]) && !isset($strSplit[3])) { // some code // A : speed 0.68 mircoseconds // B : speed 0.48 mircoseconds }

Looped isset and is_numeric :

for($i=0; $i<3;$i++) if(!isset($strSplit[$i]) || !is_numeric($strSplit[$i])) $nonNumeric = true; if(!isset($strSplit[($i+1)]) && !isset($nonNumeric)){ // some code // A : speed 0.96 mircoseconds // B : speed 1.00 mircoseconds }

count and array_filter :

if(count($strSplit) == 3 && $strSplit == array_filter($strSplit, 'is_numeric')){ // some code // A : speed 2.00 mircoseconds // B : speed 0.16 mircoseconds }
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    \$\begingroup\$ This is very clever and neat. Also nice is the fact that you can use it for any size string/array, which is what I don't like about the 'regular' approach, where you have to keep adding isset and is_numeric for every extra element. Only downside is that array functions are slower. Using isset and is_numeric seems to be the fastest (I did some speed testing): 0.81. With count instead of isset that goes up to 0.88, while your solution shows 1.50. However, this is for half a million iterations, so not a noticeable difference. \$\endgroup\$ Commented May 21, 2014 at 7:19
  • \$\begingroup\$ @kaisimir try speed testing against the string '1-foo-3-4'. The results are suprising ; ) \$\endgroup\$ Commented May 21, 2014 at 16:10
  • \$\begingroup\$ Nevermind, I edited my answer to post the results. \$\endgroup\$ Commented May 21, 2014 at 16:24
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    \$\begingroup\$ I couldn't find any speed differences myself testing against a 'wrong' string. But taking all the results together I'd say count (vs. isset) is the way to go to get the right amount of elements. The testing for numeric is more difficult. I don't like the solutions using for loops and using an extra variable, it's poorly readable. As for the static is_numeric and array_filter options: if I'd have two/three elements the is_numeric is most straightforward and the fastest. Anything more than that would mean (a lot of) extra code, so I would go for array_filter in that case. \$\endgroup\$ Commented May 22, 2014 at 14:33
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Using array functions could be the best choice. If you wanted to work on only the input that is numeric, you could use the array_filter function to get only those that are numeric. Otherwise, if you only wanted to work on the list provided all the input is numeric, a custom function would probably be the best. I have provided both styles below:

Version 1 - All Numeric

<?php // Checks to see if all input is numeric. Returns false // on the first occurance of non-numeric data. function all_numeric($list) { foreach($list as $val) { if(!is_numeric($val)) { return false; } } return true; } $expected_length = 4; $split = explode('-', '1-2-3'); // Only proceed if we have as much data as we expected and if all // the data is numeric. if(count($split) == $expected_length and all_numeric($split)) { . . . } ?>

Version 2 - Some Numeric

<?php $expected_length = 4; $split = explode('-', '1-2-3'); // Check to see if we have as much data as we expected. // No need to do anything else if not. if(count($split) == $expected_length) { // Filter the array to get only the values that are numeric. $split = array_filter($split, 'is_numeric'); . . . } ?>
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