No, no function provides the automatic cast. However you can cast with this simple hack (the cast is automatically made by PHP in internal):

float = "1.23"+0;

for generic number:

$yourNumberCasted = $yourStringNumber + 0;

With a function:

function castToNumber($genericStringNumber) { 
    return $genericStringNumber+0; 
}
$yourNumberCasted = castToNumber($yourStringNumber);

This might do the trick for you

string serialcomnum = Regex.Match(serialcom,"\\d+").ToString();
int ints = Convert.ToInt32(serialcomnum);

Another way could be

string serialcom = "$67%!$127a%";
var serialcomnum = Regex.Replace(serialcom, @"[^0-9]+", ",");
serialcomnum = serialcomnum.TrimStart(',').TrimEnd(',');
int[] serialints = serialcomnum.Split(',').Select(int.Parse).ToArray();

You can use the strval() function to convert a number to a string.

From a maintenance perspective its obvious what you are trying to do rather than some of the other more esoteric answers. Of course, it depends on your context.

$var = 5;

// Inline variable parsing
echo "I'd like {$var} waffles"; // = I'd like 5 waffles

// String concatenation 
echo "I'd like ".$var." waffles"; // I'd like 5 waffles

// The two examples above have the same end value...
// ... And so do the two below

// Explicit cast 
$items = (string)$var; // $items === "5";

// Function call
$items = strval($var); // $items === "5";

After doing a fair bit of digging, there is no solution to this in Hacklang at the moment. The only thing you have is \Stringish, an undocumented interface that covers both native strings and objects with the __toString method. It does not, however, cover int, float or bool.

Source: interfaces.hhi

tested it for 10m assignments of the number 10

One:
real    0m5.610s
user    0m5.098s
sys     0m0.220s

Two:
real    0m6.216s
user    0m5.700s
sys     0m0.213s

Three:
real    0m12.986s
user    0m11.767s
sys     0m0.489s

One seems to win

Edit: JVM is standard '/usr/bin/java' under Mac OS X 10.5

java version "1.5.0_16"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_16-b06-284)
Java HotSpot(TM) Client VM (build 1.5.0_16-133, mixed mode, sharing)

More edit:

Code as requested

public class One {
    public static void main(String[] args) {
        int someValue = 10;
        for (int i = 0; i < 10000000; i++) {
            String stringValue = Integer.toString(someValue);
        }
    }
}

case 2 and 3 similarly
run using

javac *.java; time java One; time java Two; time java Three