Extract a single integer from a string

Question

I want to extract the digits from a string that contains numbers and letters like:

"In My Cart : 11 items"

I want to extract the nu

Answer 1

Since there is only 1 numeric value to isolate in your string, I would endorse and personally use filter_var() with FILTER_SANITIZE_NUMBER_INT.

echo filter_var($string, FILTER_SANITIZE_NUMBER_INT);

A whackier technique which works because there is only 1 numeric value AND the only characters that come before the integer are alphanumeric, colon, or spaces is to use ltrim() with a character mask then cast the remaining string as an integer.

Demo

$string = "In My Cart : 11 items";
echo (int)ltrim($string, 'A..z: ');
// 11

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If for some reason there was more than one integer value and you wanted to grab the first one, then regex would be a direct technique.

Demo

echo preg_match('/\d+/', $string, $m) ? $m[0] : '';