2.14.1. Problem

2.14.2. Solution

Using BCMath:

$sum = bcadd('1234567812345678', '8765432187654321');

// $sum is now the string '9999999999999999'
print $sum;

Using GMP:

$sum = gmp_add('1234567812345678', '8765432187654321');

// $sum is now a GMP resource, not a string; use gmp_strval( ) to convert
print gmp_strval($sum);

2.14.3. Discussion

The GMP library is available as of PHP 4.0.4. While most members of the GMP family of functions accept integers and strings as arguments, they prefer to pass numbers around as resources, which are essentially pointers to the numbers. So, unlike BCMath functions, which return strings, GMP functions return only resources. You then pass the resource to any GMP function, and it acts as your number.

The only downside is when you want to view or use the resource with a non-GMP function, you need to explicitly convert it using gmp_strval( ) or gmp_intval( ).

GMP functions are liberal in what they accept. For instance:

$four = gmp_add(2, 2);            // You can pass integers
$eight = gmp_add('4', '4');       // Or strings
$twelve = gmp_add($four, $eight); // Or GMP resources
print gmp_strval($twelve);        // Prints 12

// Raising a number to a power
$pow = gmp_pow(2, 10);             // 1024

// Computing large factorials very quickly
$factorial = gmp_fact(20);         // 2432902008176640000

// Finding a GCD
$gcd = gmp_gcd (123, 456);         // 3

// Other fancy mathematical stuff
$legdendre = gmp_legendre(1, 7);   // 1

2.14.4. See Also