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up vote 5 down vote favorite
1

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

up vote 6 down vote accepted

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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1  
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. –  kasimir May 21 '14 at 7:19
    
@kaisimir try speed testing against the string '1-foo-3-4'. The results are suprising ; ) –  Ben A. Noone May 21 '14 at 16:10
    
Nevermind, I edited my answer to post the results. –  Ben A. Noone May 21 '14 at 16:24
1  
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. –  kasimir May 22 '14 at 14:33
up vote 2 down vote

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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