PHP - Array size returns 1?

Question

Under Return Values for Count()

Returns the number of elements in var. If var is not an array or an object with implemented Countable interface, 1 will be returned. There is one exception, if var is NULL, 0 will be returned.

I have a string which is filled with letters and numbers and I'm using preg_match_all() to extract those numbers. As I recall preg_match_all fills the contents of the array given in the 3rd parameter with the results. Why does it return 1?

What am I doing wrong in my code?

$string = "9hsfgh563452";
preg_match_all("/[0-9]/",$string,$matches);

echo "Array size: " . count($matches)."</br>"; //Returns 1
echo "Array size: " . sizeof($matches)."</br>"; //Returns 1
print_r($matches);

I would like to sum the contents of the array (which is all the numbers returned in the string) array_sum() didn't work ; it is a string array and I don't know how to convert it to an int array because I'm not using any delimiters like ' , ' and such. Is there a more efficient way in doing this?

Help appreciated.

Answer 1

The count is 1 because $matches is an array which contains another array inside. Specifically, $matches[0] is an array that contains each match of the zero-th capturing group (the whole regular expression).

That is, $matches looks like this:

Array
(
    [0] => Array  // The key "0" means that matches for the whole regex follow
        (
            [0] => 9   // and here are all the single-character matches
            [1] => 5
            [2] => 6
            [3] => 3
            [4] => 4
            [5] => 5
            [6] => 2
        )

)

Answer 2

The result of preg_match_all is actually an array of an array:

Array
(
    [0] => Array
        (
            [0] => 9
            [1] => 5
            [2] => 6
            [3] => 3
            [4] => 4
            [5] => 5
            [6] => 2
        )
)

So you'll need to do something like:

echo "Array size: " . count($matches[0]);

echo "Array sum: " . array_sum($matches[0]);

Answer 3

This is due to the way preg_match_all returns results. Its main array elements are the preg brackets (expression matches), whilst the contents of them are what you matched.

In your case, you have no sub-expressions. The array will therefore only have one element - and that element will contain all your digits.

To sum them up, simply do this:

$sum = 0;
$j = count($matches[0]);
for ($i = 0; i < $j; ++$i) {
  $sum += (int)$matches[0][$i];
}

Answer 4

Try using $matches[0] instead of $matches (returns 7).

Then if you want to sum all the numbers you can use the foreach function