Just like the normal numeric operations you would usually do, but with numbers of any size.
<?php
$integerNumber = Integer::createByInt(1);
$smallNumber = Integer::createByString('1');
$largeNumber = Integer::createByString('987654321234567898765432123456789');
// A really large number that as primitive type might throw a number in scientific notation or infinity.
$reallyLargeNumber = Integer::createByString('12345678987654321234567898765432123456789876543212345678987654321234567898765432123456789876543212345678987654321234567898765432123456789876543212345678987654321234567898765432123456789876543212345678987654321234567898765432123456789876543212345678987654321234567898765432123456789876543212345678987654321234567898765432123456789876543212345678987654321234567898765432123456789876543212345678987654321234567898765432123456789876543212345678987654321234567898765432123456789876543212345678987654321');
<?php
$a = Integer::createByString('1234567898765432123456789876543212345678987654321');
$b = Integer::createByString('987654321234567898765432123456789');
// $c = 1234567898765433111111111111111111111111111111110
$c = $a->add($b);
<?php
$a = Integer::createByString('1234567898765432123456789876543212345678987654321');
$b = Integer::createByString('987654321234567898765432123456789');
// $c = 1234567898765431135802468641975313580246864197532
$c = $a->subtract($b);
$a = Integer::createByString('987654321234567898765432123456789');
$b = Integer::createByString('1234567898765432123456789876543212345678987654321');
// $c = -1234567898765431135802468641975313580246864197532
$c = $a->subtract($b);
<?php
$a = Integer::createByString('999999999999');
$b = Integer::createByString('789');
// $c = 788999999999211
$c = $a->multiplyBy($b);
$a = Integer::createByString('1234567898765432123456789876543212345678987654321');
$b = Integer::createByString('987654321234567898765432123456789');
// $c = 1219326320073159600060966114921506736777910409998442005792202408166072245112635269
$c = $a->multiplyBy($b);
<?php
$dividend = Integer::createByString('987654321234567898765432123456789');
$divisor = Integer::createByString('12345678987654321');
// $quotient = 80000000180000000
$quotient = $dividend->divideBy($divisor);
<?php
$dividend = Integer::createByString("1234567890123456789");
$divisor = Integer::createByString("9876543210");
// $module = 8626543209
$module = $dividend->mod($divisor);
<?php
$a = Integer::createByString("123456789012345678901234567890");
$b = Integer::createByString("987654321");
// true
$comparison = $a->greaterThan($b);
$a = Integer::createByString("987654321");
$b = Integer::createByString("123456789012345678901234567890");
// false
$comparison = $a->greaterThan($b);
<?php
$a = Integer::createByString("1500");
$b = Integer::createByString("1492");
// true
$comparison = $a->greaterOrEqualTo($b);
$a = Integer::createByString("1234567890");
$b = Integer::createByString("1234567890");
// true
$comparison = $a->greaterOrEqualTo($b);
$a = Integer::createByString("1234");
$b = Integer::createByString("1234567890");
// false
$comparison = $a->greaterOrEqualTo($b);