How we calculate change on the trade

gistfile1.txt

/*
  *
  * HEY KEVIN!
  *
  * OKAY .... SO HERE's HOW TO READ THIS SO YOU CAN CHECK MY LOGIC
  * I HAVE TO ALWAYS TRANSLATE OUR EXPLAINATIONS INTO CODE
  * AND THEN I HAVE TO ACCOUNT FOR DATA THAT MAY/MAY NOT BE THERE
  * SO HERE'S WHERE YOUR LAST EMAIL ENDED UP...
  *
  * TO READ THIS:
  * CONSIDER: $this = "a given property"
  * AND "//" is a comment ... the rest is the live code
  *
*/

// Let's set some initial values ... we'll override these later
$change = [
    'amount' => 0,
    'percentage' => 0,
    'positive' => true,
];

/* 
    First, let's find a starting value for a given property
*/

// Get yesterday's last trading value value
$yesterdaysLastTrade = $this->yesterdaysTrades->last();

// IF there was a trade yesterday, 
if ($yesterdaysLastTrade) 
{
    // Get it's price and use it as today's starting value
    $todaysStartingValue = $yesterdaysLastTrade->price_per_share;

// IF there was no trade yesterday
} else {

    // Get the last price that it traded at before yesterday
    $lastKnownPriceBeforeToday = $this->allTradesBeforeYesterday->last();

    // If we find a known price before today
    if ($lastKnownPriceBeforeToday)
    {
        // Use it as starting value
        $todaysStartingValue = $lastKnownPriceBeforeToday->price_per_share;

    // But if we don't find a last known price (i.e., it's never traded)
    } else {

        // use the initial trade value from the admin panel
        $todaysStartingValue = $this->masterInfo->initial_trade_value;
    }

}

/* 
    Now that we have a starting value, let's see if there's been any trades today
*/

// Get today's trade
$todaysTrade = $this->todaysTrades->last();

// If there was a trade today
if (count($todaysTrade) > 0)
{

    // Okay, now that we have a starting value... and a trade for today ... we can begin to do some maths
    $amountOfChange = $todaysTrade->price_per_share - $todaysStartingValue;

    // If the change is positive, it will be an integer greater than or equal to 0
    // this will make sure to tell it to be red or green            
    if ( (int)$amountOfChange == $amountOfChange && (int)$amountOfChange >= 0 )
    {
        $change['positive'] = true;
    } else {
        $change['positive'] = false;
    }

    // Format the response ... first the amount
    $change['amount'] = $amountOfChange;

    // then we get it as a percent where amount of change times 100 is divided by the starting value
    $changeAsPercent = (int)$amountOfChange * 100 / $todaysStartingValue;

    // then round it to a whole percent
    $change['percentage'] = (int)number_format($changeAsPercent,0);

// Else if there hasn't been any trades today, the change is zero
} else {

    // so we do nothing
}

// Return the change information
return $change;