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POStock option price variations by users orders (buy/sell)
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copied!<p>Following this question <a href="https://stackoverflow.com/questions/9353938/generate-a-fictitious-stock-option-price-variation">Generate a fictitious stock option price variation</a></p> <p>I wish to simulate that the price change, while users gives an order of buy or sell, like the real stock exchange. (I make a user case to help you to understand.)</p> <p><strong>Initial state "Stock option example"</strong> :</p> <p>Company X, price of the stock option $20,000</p> <p>A CRON task makes the price variation each second, with this PHP script :</p> <pre><code>function stockVariation($price,$max_up,$max_down) { // Variation calculate, with volatility max (10 to 100) $ratio=(mt_rand(0,$max_up)-mt_rand(0,$max_down))/10000; // New price $price+=$ratio; return round($price,5); } </code></pre> <p>Volatility is made by random news which makes $max_up > $max_down or $max_up < max_down for a random time. Between, $max_up = $max_down.</p> <p>Result in picture (1hour by minutes) <img src="https://i.stack.imgur.com/yseVl.jpg" alt="Stock option price variation"></p> <p><strong>User case "Buy example"</strong> :</p> <ul> <li>A user send an order to buy 1000 of this option at $18,000</li> <li>The system store the order in database</li> <li>A CRON task verify each minute, if the price was <= to a buy order, the last minute</li> <li>When the price of this option <= to this order, the user gets this stock option.</li> </ul> <p><strong>User case "Sell example"</strong> :</p> <ul> <li>A user send an order to sell 1000 of this option at $22,000</li> <li>The system store the order in database</li> <li>A CRON task verify each minute, if the price was >= to a sell order, the last minute</li> <li>When the price of this option >= to this order, the user sells this stock option.</li> </ul> <p><strong>My problem</strong></p> <p>It works fine, but it is not a real variation of a stock exchange market.</p> <p><strong>My question</strong></p> <p>How to make the price variation by the prices and quantities of the orders ?</p> <p><em>Like the "law of supply and demand".</em></p> <p>For example (<strong>edit regarding Peter answer</strong>) :</p> <pre><code>function stockOrder($orderPrice,$orderQuantity,$type)//$type= buy or sell { // Record the order in database (ok) // Compare with other orders (ok) // $orderPrice<=$dbSellPrice or $orderPrice>=$dbBuyPrice if checks // Buy and sell at the best prices // for quantities available holded by users (ok) // Record/update the holding of the stock (ok) // Update the price of the stock end if } </code></pre> <p>Perhaps I'm a little bit crazy to think that it could be possible to automatize that, but I believe in it, any help will be greatly appreciated.</p>

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