Lesson 8 - PHP & Yahoo Finance API

php-yahoo-finance.php

<?php namespace SS\Stock;

use DB, File, Cache;

class Stock {

    public function __construct()
    {
        ini_set("memory_limit", "-1");
        set_time_limit(0);
    }

    /**
     * Update the stock streaks after the market has closed
     *
     * @param $overwrite (whether to update all data from beginning)
     * @return void
     */

    public function updateStreaks($overwrite = false)
    {
        $date = DB::table('summaries')->max('date');

        $stocks = DB::table('stocks')->select('symbol')->orderBy('symbol', 'asc')->get();

        foreach ($stocks as $stock)
        {
            $stored = DB::table('stocks')
                ->where('symbol', $stock->symbol)
                ->where('streak_stored', $date)
                ->first();

            if ($stored && !$overwrite) continue;
                
            $days = DB::table('summaries')
                ->select('close', 'volume')
                ->where('symbol', $stock->symbol)
                ->orderBy('date', 'desc')
                ->limit(20)
                ->get();

            $streak = 0;

            for ($i = 0; $i < count($days); $i++)
            {
                // if we're at the earliest day recorded for a stock, the streak is over
                if ( ! isset($days[$i + 1])) break;

                // if the next days price is the same as the current, the streak is over
                if ($days[$i]->close === $days[$i + 1]->close) break;

                // one time check for the first iteration
                if ($i === 0)
                {
                    if ($days[$i] > $days[$i + 1])
                    {
                        $streak++; continue;
                    }

                    if ($days[$i] < $days[$i + 1])
                    {
                        $streak--; continue;
                    }
                }

                // check if the winning streak is over or not
                if ($streak > 0)
                {
                    // if current day's close is less than the day before it, the winning streak is over
                    if ($days[$i]->close < $days[$i + 1]->close) break;
                    
                    // the winning streak continues
                    $streak++;
                }
                elseif ($streak < 0)
                {
                    // if the current day's close is more than the day before it, the losing streak is over
                    if ($days[$i]->close > $days[$i + 1]->close) break;
                    
                    // the losing streak continues
                    $streak--;
                }
            }

            $amount = $this->calculateMovePercentage($days, $streak);

            $volume = $this->calculateStreakVolume($days, $streak);

            DB::table('stocks')
                ->where('symbol', $stock->symbol)
                ->update([
                    'streak' => $streak,
                    'move_percentage' => $amount,
                    'streak_volume' => $volume,
                    'streak_stored' => $date,
                ]);

            print "Symbol: " . $stock->symbol . " # Streak: " . $streak . " # ";
            print "Amount: " . $amount        . " # Volume: " . $volume . "\n";
        }
    }

    /**
     * Update the stock streaks after the market has closed
     *
     * @param  array $days (daily summaries)
     * @param  int   $days (streak)
     * @return int         (shares traded volume)
     */

    public function calculateStreakVolume(array $days, $streak)
    {
        $daysOnStreak = array_slice($days, 0, abs($streak));

        $volume = 0;

        foreach ($daysOnStreak as $day) {
            $volume += $day->volume;
        }

        return $volume;
    }

    /**
     * Get the percentage the stock moved over the streak's duration
     *
     * @param  array  $days (daily summaries)
     * @param  int    $days (streak)
     * @return double       (move percentage)
     */

    public function calculateMovePercentage(array $days, $streak)
    {
        if ($streak == 0) return 0;

        $days = array_slice($days, 0, abs($streak) + 1);

        return round((($days[0]->close / end($days)->close) - 1) * 100, 2);
    }
}

cool code!