php string to int

intval($string);

s = "123";
echo intval(s); // 123

s = "hello";
echo intval(s);	//0

$num = "3.14"; 
$int = (int)$num;//string to int
$float = (float)$num;//string to float

$num = "3.14";
$int = (int)$num;

intval ( mixed $var [, int $base = 10 ] ) : int