I'm relatively experienced with Java and C++ so picking up PHP wasn't too difficult. I wanted to get some feedback on my first PHP class. There's nothing extremely complicated as of now, but its nice to get feedback.
The only part I feel that I will definitely get feedback is for the readCSV() function. I made it specifically this way as I need to read the csv file row by row for each column rather than column by column. I couldn't figure out how to do that with foreach so I had to revert to the regular for loop.
<?php
/**
* Description of Refrigerant
* Class for the refrigerant. Stores information about the refrigerant as well
* as functions to calculate values including but not limited to
* SEI, COP, Enthalpy, Pressure temp
* @author Eric
*/
class Refrigerant {
/*
* ===================================================================
* ===================================================================
* Variable Declaration
* ===================================================================
* ===================================================================
*/
// public variables to be accessed straight from the object
public $refrigerantType; // Type of refrigerant -> a string value
// "r22" "r404a" etc
// protected variables only to be accessed within the class and sub classes
// Arrays of charts, temperature[key] will link to the pressure[key]
protected $temperature; // temperature chart
protected $pressure; // pressure chart
protected $liquidEnthalpy; // liquid enthalpy chart
protected $vaporEnthalpy; // vapor enthalpy chart
protected $ratio; // ratio of the liquid, suction and discharge factors
/*
* ===================================================================
* ===================================================================
* Constructor & Destructor
* ===================================================================
* ===================================================================
*/
/**
* Constructor for the refrigerant class
* Only requires a type of refrigerant to be declared
* @param string $rtype ex. "r22", "r404a"
*/
function __construct($rtype) {
$this->refrigerantType = $rtype;
$this->temperature = [];
$this->pressure = [];
$this->liquidEnthalpy = [];
$this->vaporEnthalpy = [];
$this->ratio = [];
}
/*
* ===================================================================
* ===================================================================
* Reading CSV Functions
* ===================================================================
* ===================================================================
*/
/**
* Attempts to read a .csv file with the specific delimeter character
* @param string $file filename to open
* @param char $delimiter delimter to use
*/
function readCSV($file, $delimiter) {
// Read the file into a 2D array and store it in data
$data = $this->get2DArrayFromCsv($file, $delimiter);
// Read the data column by column and save the information based on the
// header of the column
// Find how many columns we are reading
$cols = count($data[0]);
for ($col = 0; $col < $cols; $col++) {
// For each column
$rows = count($data);
for ($row = 0; $row < $rows; $row++) {
// This will not execute anything if the cell is empty
if ($data[$row][$col] == "") {
break;
}
// Dont parse any of the header data
if ($row > 0) {
switch ($data[0][$col]) {
case 'Temperature':
array_push($this->temperature, $data[$row][$col]);
break;
case 'Pressure':
array_push($this->pressure, $data[$row][$col]);
break;
case 'Liquid Ent':
array_push($this->liquidEnthalpy, $data[$row][$col]);
break;
case 'Vapor Ent':
array_push($this->vaporEnthalpy, $data[$row][$col]);
break;
case 'Liquid':
$this->ratio = $this->array_push_assoc($this->ratio, 'Liquid', (float) $data[$row][$col]);
break;
case 'Discharge':
$this->ratio = $this->array_push_assoc($this->ratio, 'Discharge', (float) $data[$row][$col]);
break;
case 'Suction':
$this->ratio = $this->array_push_assoc($this->ratio, 'Suction', (float) $data[$row][$col]);
break;
}
}
}
/* Only if some rows will have less columns than the previous
if ($col + 1 < count($data)) {
$cols = count($data[$col + 1]);
} */
}
}
/**
* Reads the csv file and returns the data in a 2d array to be parsed
* @param string $file file name
* @param string $delimiter delimeter
* @return array 2d array of the data
*/
private function get2DArrayFromCsv($file, $delimiter) {
if (($handle = fopen($file, "r")) !== FALSE) {
$i = 0;
while (($lineArray = fgetcsv($handle, 4000, $delimiter)) !== FALSE) {
for ($j = 0; $j < count($lineArray); $j++) {
$data2DArray[$i][$j] = $lineArray[$j];
}
$i++;
}
fclose($handle);
}
return $data2DArray;
}
/*
* ===================================================================
* ===================================================================
* Calculating Values Functions
* ===================================================================
* ===================================================================
*/
/**
* Finds the pressure temperature based on the pressure passed to the
* function. Accesses the temperature and pressure charts to find the new
* temperature value using interpolation
* @param double $newPressure pressure value
* @return double temperature corresponding to the new pressure
*/
function pressureTemp($newPressure) {
$values = $this->findBoundValues($this->pressure, $this->temperature, $newPressure);
// interpolate the values
$lowPressure = $values[0];
$highPressure = $values[1];
$lowTemp = $values[2];
$highTemp = $values[3];
if ($values[4] == "int") {
$temp = $this->interpolate($lowPressure, $highPressure, $lowTemp, $highTemp, $newPressure);
} else if ($values[4] == "ext") {
$temp = $this->extrapolate($lowPressure, $highPressure, $lowTemp, $highTemp, $newPressure);
}
// We want to find temp, so first two values are pressure
// second two are temperatures, and last is the new presssure
/*
print "{$lowPressure} -- {$lowTemp}<br>";
print "{$newPressure} -- {$temp}<br>";
print "{$highPressure} -- {$highTemp}<br>";
*
*/
return $temp;
}
/**
* Finds the subcooling value by subtracting the dlt from sat
* Used by the liquid state
* @param double $sat Saturating condensing temperature
* @param double $dlt Drop leg temperature
* @return double subcooling value
*/
function subcooling($sat, $dlt) {
return $sat - $dlt;
}
/**
* Finds the superheat value by subtracting the state pressure temp from
* the state temperature
* Discharge temperature - Discharge pressure temperature
* Suction temperature - Suction pressure temperature
* @param double $stateTemp discharge/suction temperature
* @param double $statePressureTemp discharge/suction pressure temperature
* @return double superheat value
*/
function superheat($stateTemp, $statePressureTemp) {
return $stateTemp - $statePressureTemp;
}
/**
* Finds the enthalpy value of the given state, using temp1 and temp2 values
* @param string $state Liquid, Discharge, Suction
* @param double $temp1 Pressure used to find the pressure temp
* @param double $temp2 for liquid drop leg temp
* @return double enthalpy value for the specific state
*/
function enthalpy($state, $temp1, $temp2) {
switch ($state) {
case 'Liquid':
// Liquid - Subcooling
$sct = $this->pressureTemp($temp1);
$values = $this->findBoundValues($this->temperature, $this->liquidEnthalpy, $sct);
$intVal = $this->interpolate($values[0], $values[1], $values[2], $values[3], $values[4]);
return $intVal - ($this->subcooling($sct, $temp2) * $this->ratio['Liquid']);
//break;
case 'Discharge':
// Discharge - Superheat
$dsct = $this->pressureTemp($temp1);
$values = $this->findBoundValues($this->temperature, $this->vaporEnthalpy, $dsct);
$intVal = $this->interpolate($values[0], $values[1], $values[2], $values[3], $values[4]);
return $intVal + ($this->superheat($dsct, $temp2) * $this->ratio['Discharge']);
case 'Suction':
// Suction - Superheat
$sst = $this->pressureTemp($temp1);
$values = $this->findBoundValues($this->temperature, $this->vaporEnthalpy, $sst);
$intVal = $this->interpolate($values[0], $values[1], $values[2], $values[3], $values[4]);
return $intVal + ($this->superheat($sst, $temp2) * $this->ratio['Discharge']);
default:
echo "enthalpy default case";
}
}
/**
* Finds the three enthalpy values, then uses them to calculate the COP
*
* @param double $temp1 pressure used to find the pressure temp
* @param double $temp2
* @return double COP value
*/
function COP($temp1, $temp2) {
$liquid = $this->enthalpy('Liquid', $temp1, $temp2);
$suction = $this->enthalpy('Suction', $temp1, $temp2);
$discharge = $this->enthalpy('Discharge', $temp1, $temp2);
return ($suction - $liquid) / ($discharge - $liquid);
}
/**
*
* @param type $outdoorTemp outdoor air temp in celsius
* @param double $temp1 pressure used to find the pressure temp
* @param double $temp2
* @return double SEI value
*/
function SEI($outdoorTemp, $temp1, $temp2) {
// Convert outdoor air temp to kelvin
$a = $outdoorTemp + 273;
$d = $this->enthalpy('Suction', $temp1, $temp2) + 273;
$t = $d / ($a - $d);
$cop = $this->COP($temp1, $temp2);
return $cop / $t * 100;
}
/*
* ===================================================================
* ===================================================================
* Functions used by Calculations
* ===================================================================
* ===================================================================
*/
/**
* Finds the lower and upper bounds of the two variables being used for
* interpolation or extrapolation calculations. It also returns if it
* is a interpolation or extrapolation calculation
* @param array $xArray array of values which x actual will be in
* @param array $yArray array of values which will contain the coressponding value to xActual
* @param double $xActual the actual value we are using to find the coressponding value
* @return array values stored 0 through 4
* 0 - double - lower bound of xArray
* 1 - double - higher bound of xArray
* 2 - double - lower bound of yArray
* 3 - double - higher bound of yArray
* 4 - string - ext or int for extrapolation or interpolation
*/
function findBoundValues($xArray, $yArray, $xActual) {
$values = [];
// Check to see if the new pressure is below the lowest known point
// or if it is above the highest known point
$numPoints = count($xArray);
// If the new pressure is lower than the lowest point we have
if ($xActual <= $xArray[0]) {
// Set the lowest and highest pressure/temperatures to the first
// and second lowest and extrapolate from there
$values[0] = $xArray[0];
$values[1] = $xArray[1];
$values[2] = $yArray[0];
$values[3] = $yArray[1];
$values[4] = "ext";
return $values;
} else if ($xActual >= $xArray[$numPoints - 1]) {
// If the new pressure is higher than the highest point we have
// Set the lowest and highest pressure/temperatures to the first
// and second lowest and extrapolate from there
$values[0] = $xArray[$numPoints - 2];
$values[1] = $xArray[$numPoints - 1];
$values[2] = $yArray[$numPoints - 2];
$values[3] = $yArray[$numPoints - 1];
$values[4] = "ext";
return $values;
} else {
// New pressure point is somewhere in the range of values on the chart
foreach ($xArray as $key => $value) {
// The current value is higher than the new pressure, so set
// the higher bound values, lower bound will already be set
if ($value > $xActual) {
$values[1] = $value;
$values[3] = $yArray[$key];
break;
} else {
// Every time we pass a point that is lower than the new pressure
// we set the lower bound values
$values[0] = $value;
$values[2] = $yArray[$key];
}
}
$values[4] = "int";
return $values;
}
}
/**
* interpolate function
* @param double $x1 low end of left side
* @param double $x2 high end of left side
* @param double $y1 low end of right side
* @param double $y2 high end of right side
* @param double $xActual value inbetween x1 and x2
* @return double the value matching the xActual value on
* the scale of the Y values
*/
function interpolate($x1, $x2, $y1, $y2, $xActual) {
$xDiff = abs($x1 - $x2);
$yDiff = abs($y1 - $y2);
$xPer = abs($x1 - $xActual) / abs($xDiff);
$newY = $y1 + ($xPer * $yDiff);
return $newY;
}
/**
* extrapolate function - the new point is not
* @param double $x1 low end of left side
* @param double $x2 high end of left side
* @param double $y1 low end of right side
* @param double $y2 high end of right side
* @param double $xActual value inbetween x1 and x2
* @return double the value matching the xActual value on
* the scale of the Y values
*/
function extrapolate($x1, $x2, $y1, $y2, $xActual) {
$xDiff = abs($x1 - $x2);
$yDiff = abs($y1 - $y2);
$xPer = abs($x1 - $xActual) / abs($xDiff);
// If the actual value is below, we subtract it from the lower value
// If the acutal value is higher, we add it to the higher value
if ($xActual <= $x1) {
$newY = $y1 - ($xPer * $yDiff);
} else if ($xActual >= $x2) {
$newY = $y2 + ($xPer * $yDiff);
}
return $newY;
}
/*
* ===================================================================
* ===================================================================
* Quality of Life (QoL) Functions
* ===================================================================
* ===================================================================
*/
/**
* Adds a value to an associative array
* @param array $array array to add a value to
* @param string $key key of the array to add to
* @param double $value value to be added
* @return array the array being modified
*/
function array_push_assoc($array, $key, $value) {
$array[$key] = $value;
return $array;
}
}
