Body Mass Index

Calculating Body Mass Index (BMI) is quite simple and this small class makes it even easier. The class uses two calculations, one for imperial measurements, and one for metric, which can be set easily.

If set to metric, the weight is a measurement in kilograms and the height is a measurement in meters.

If set the imperial, the weight is a measurement in pounds and the height is a measurement in inches.

When a numeric value for the BMI has been calculated, a scale is used to detirmine where the value a lays.

Below 18.5: Underweight
18.5 - 24.9: Normal
25 - 29.9: Overweight
30 and Above: Obese



<?php
class bodyMassIndex{

    /*
     * @string the bmi index
     */
    public $bmi_index;

    /*
     * @float bmi index number
     */
    public $bmi;

    /*
     *
     * @set variables
     *
     * @access public
     *
     * @param mixed $name
     *
     * @param mixed $value
     *
     */
    public function __set($name, $value)
    {
        switch ( $name )
        {
            case 'weight':
            if(!is_numeric($value))
            {
                throw new Exception( "$name is Invalid" );
            }
            break;

            case 'height':
            if(!is_numeric($value))
            {
                throw new Exception( "$name $value is Invalid" );
            }
            break;

            case 'units':
            if(!is_string($value))
            {
                throw new Exception( "$name $value is Invalid" );
            }
            break;
            }
        $this->$name = $value;
    }

    /**
     *
     * Returns the value of the property $name.
     *
     * @throws Exception if the property does not exist.
     *
     * @param string $name
     *
     */
    public function __get( $name )
    {
        switch ( $name )
        {
            case 'height':
            return $this->height;
            break;

            case 'weight':
            return $this->weight;
            break;

            case 'units':
            return $this->units;
            break;
        }
        throw new Exception("Property Not Found $name");
    }


    public function calculateBMI()
    {
        if($this->units == 'imperial')
        {
            /*** imperial ***/
            $bmi = $this->weight / pow($this->height,2) * 703;
        }
        elseif($this->units == 'metric')
        {
            /*** metric ***/
            $bmi = $this->weight / pow($this->height,2);
        }
        else
        {
            throw new Exception("Invalid Unit");
        }
        /*** assign the bmi ***/
        $this->bmi = round($bmi, 2);
        $this->bmi_index = $this->bmiIndex();
    }

    /*
     * @the bmi index
     *
     * @access public
     *
     * @return string
     *
     */
    public function bmiIndex()
    {
        if($this->bmi < 18.5)
        {
            return 'Underweight';
        }
        elseif($this->bmi <= 24.9 && $this->bmi >= 18.5)
        {
            return 'Normal';
        }
        elseif($this->bmi <= 29.9 && $this->bmi >= 25)
        {
            return 'Overweight';
        }
        elseif($this->bmi <= 30)
        {
            return 'Obese';
        }
        else
        {
            throw new Exception("Out Of Range");
        }
    }

} /*** end of class ***/

Example Usage



<?php

try
{
    /*** a new bodyMassIndex object ***/
    $bmi = new bodyMassIndex;

    /*** set the units ***/
    $bmi->units = 'metric';

    /*** height in meters ***/
    $bmi->height = 1.98;

    /*** weight in kilograms ***/
    $bmi->weight = 78;

    /*** calculate the bmi ***/
    $bmi->calculateBMI();

    /*** echo numerical index ***/
    echo $bmi->bmi.'<br />';

    /*** prognosis ***/
    echo $bmi->bmi_index;
}
catch(Exception $e)
{
    echo $e->getMessage();
}

?>

Demonstration

20.72
Normal