# FinLib - a PHP Library With Financial Functions and Calculators

**Current version: 0.1.7**

FinLib is a library with PHP functions and classes for performing financial calculations and equations. Please visit test.php in your browser to have a look at quick demo. The library consists of two main classes - Calculator and Equator.

## The Calculator Class

The Calculator class lets you create and display financial calculators in your site. Each of the calculators is a method of the class. It receives an array of input parameters (typically you would just sent it the $_POST), and returns an array containing the results. To use the class simply include the file and create an instance:

include('calculator.php');

$_calculator = new Calculator();

Below are the currently available calculators:

### Home Affordability Calculator

Call method **home_affordabilit($input)**.

Requires the following $input array:

- "tax" : Annual property taxes

- "insurance" : Annual insurance

- "income_per_period" : Gross annual income

- "monthly_debt" : Monthly debt

- "interest" : Mortgage loan rate

- "downpayment": Downpayment amount

Returns the following output array:

- "min_price" : Minimum house price (conservative)

- "max_price" : Minimum house price (aggressive)

- "min_loan" : Loan amount (conservative)

- "max_loan" : Loan amount (aggressive)

- "min_payment" : Monthly mortgage payment (conservative)

- "max_payment" : Monthly mortgage payment (aggressive)

- "taxes_and_insurance" : Taxes and insurance

- "min_total" : Total monthly payment (conservative)

- "max_total" : Total monthly payment (aggressive)

### Monthly Mortgage Payment Calculator

Call method **mortgage_payment($input)**.

Requires the following $input array:

- "years" - loan term in years

- "interest" - loan interest

- "loan_amount" - loan amount

- "annual_tax" - anual tax

- "annual_insurance" - annual insurance

Returns the following output array:

- "monthly_principal" - Monthly Principal + Interest

- "monthly_tax" - Monthly tax

- "monthly_insurance" - Monthly insurance

- "total" - Total monthly payment

### Simple Retirement Calculator

Call method **simple_retirement($input)**.

Requires the following $input array:

- "principal" - the current principal

- "addition" - pre-retirement addition

- "growyears" - years to grow

- "rate" - grow rate

- "pyears" - years to pay out

- "prate" - in retirement grow rate

Returns a single value - the annual retirement income.

## The Equator Class

This class executes several important financial equations. Unlike with the Calculator class, normally you would use several of the methods of the Equator to build a single calculator or other financial program. To use the class simply include the file and create an instance:

include('equator.php');

$_equator = new Equator();

Below are the currently available equations:

### Effective Interest Rate Equation

Call method **effective_interest($input)**.

Requires the following $input array:

- "nominal_interest" - nominal interest rate

- "compounding_frequency" - the compounding frequency per year

- "payments_per_year" - number of payments per year.

Retuns single value - the interest rate.

### Future Value of a Single Sum

Call method **future_value($input)**.

Requires the following $input array:

- "present_value" - the present value (the sum)

- "interest" - the interest rate

- "periods" - the number of periods.

Returns single value - the future value of the sum.

### Future Value With Compounding

Call method **future_value_compounded($input)**.

Requires the following $input array:

- "present_value" - the present value (the sum)

- "interest" - the interest rate

- "periods" - the number of periods
- "compounding_frequency" - the compounding frequency per period

Returns single value - the future value of the sum.

### Future Value Of Annuity

Call method **future_value_annuity($input)**.

Requires the following $input array:

- "periodic_payment" - payment per period

- "interest" - the interest rate

- "periods" - the number of periods

Returns single value - the future value of the annuity.

### Future Value Of Annuity Due

Call method **future_value_annuity_due($input)**.

Requires the following $input array:

- "periodic_payment" - payment per period

- "interest" - the interest rate

- "periods" - the number of periods

Returns single value - the future value of the annuity due.

### Monthly Payment (On loan, mortgage etc)

Call method **monthly_payment($input)**.

Requires the following $input array:

- "amount" - the loan amount

- "interest" - the interest rate

- "periods" - the number of periods

Returns single value - the monthly payment amount.

### Present Value of Investment Made in the Future

Call method **present_value($input)**.

Requires the following $input array:

- "future_value" - the future value of the investment

- "interest" - the interest rate

- "periods" - the number of periods

Returns single value - the present value of the investment.

### Present Value of Investment Made in the Future With Compounding

Call method **present_value_compounded($input)**.

Requires the following $input array:

- "future_value" - the future value of the investment

- "interest" - the interest rate

- "periods" - the number of periods

Returns single value - the present value of the investment.

### Perpetuity

Call method **perpetuity($input)**.

Requires the following $input array:

- "payment" - the payment amount

- "interest" - the interest rate

Returns single value - the perpetuity.

### Expected Rate of Return

Call method **ERR($vals)**.

Accepts array of arrays ((probability, ROI), (probability, ROI)...)

Returns single value - the expected rate of return.

Published at Nov, 27 '13 , Read 68591 times.

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