在字符串中查找素数和复合数

Question

I have the following randomly generated string:

$text = 's$bp4q1hsq3@g88nsjm5hr#i9#3078e2m';

What I need is to take all integers from it and classify them as either prime or composite numbers and estimate their sum. All numbers should be assumed that are one digit so this shortens the values to only four per each group:

$primes     = array(2, 3, 5, 7);
$composites = array(4, 6, 8, 9);

This means: Primes: 5, 3, 3, 2 = 13 and Composites: 4, 8, 8, 9, 8 = 37 as duplicate numbers also count.

I have tried grabbing the numbers like so:

$asArray = str_split($text);

foreach ($asArray as $element) {
    if (is_int($element)) {
        echo $element;
    }
}

But it seems to end up in a blank page. So my question is how can I find out the numbers in a string and then classify them as either prime or composite?

Answer 1

Here you have the sum of the primes and composites:

$text = 's$bp4q1hsq3@g88nsjm5hr#i9#3078e2m';
$primes     = array(2, 3, 5, 7);

$sum_primes = $sum_composites = 0; 

preg_match_all("/\d/", $text, $matches);

foreach($matches[0] as $number)
{
    if (in_array($number, $primes))
        $sum_primes += $number; 
    else
        $sum_composites += $number; 
} 

echo "Sum of primes: ".$sum_primes."
";
echo "Sum of composites: ".$sum_composites."
";

It would print,

Sum of primes: 20
Sum of composites: 38