Hola @Luminis :)
Este código puede servirte:
Código PHP:
Ver original$str1 = 'gained 1 point';
$number1 = implode(' ', $matches[0]);
$str2 = 'gained 100 points';
$number2 = implode(' ', $matches[0]);
$str3 = 'gained 1000 points';
$number3 = implode(' ', $matches[0]);
echo $number1 + $number2 + $number3;
Saludos!