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docs/ccxt/wiki/examples/php/arbitrage-pairs.md

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+- [Arbitrage Pairs](./examples/php/)
+
+
+ ```php
+ <?php
+
+include './ccxt.php';
+include 'Console/Table.php'; // pear-install it from here: https://pear.php.net/package/Console_Table/
+
+date_default_timezone_set('UTC');
+
+function style ($s, $style) { return $style . $s . "\033[0m"; }
+function green     ($s) { return style ($s, "\033[92m"); }
+function blue      ($s) { return style ($s, "\033[94m"); }
+function yellow    ($s) { return style ($s, "\033[93m"); }
+function red       ($s) { return style ($s, "\033[91m"); }
+function pink      ($s) { return style ($s, "\033[95m"); }
+function bold      ($s) { return style ($s, "\033[1m"); }
+function underline ($s) { return style ($s, "\033[4m"); }
+function dump ($s) { echo implode (' ', func_get_args ()) . "\n"; }
+
+function print_supported_exchanges () {
+    $exchanges = \ccxt\Exchange::$exchanges;
+    dump ('Supported exchanges:', green (implode (', ', $exchanges)));
+}
+
+function flatten ($array) {
+    return array_reduce ($array, function ($acc, $item) {
+        return array_merge ($acc, is_array ($item) ? flatten ($item) : [$item]);
+    }, []);
+}
+
+function tabulate ($headers, $rows) {
+    $tbl = new Console_Table();
+    $tbl->setHeaders ($headers);
+    $tbl->addData ($rows);
+    return $tbl->getTable ();
+}
+
+function pairs_table_helper ($pair) {
+    return array_values ($pair);
+}
+
+$proxies = array (
+    '', // no proxy by default
+    'https://crossorigin.me/',
+    'https://cors-anywhere.herokuapp.com/',
+);
+
+$max_retries = count ($proxies);
+$ids = array_slice ($argv, 1);
+$exchanges = array ();
+$min_exchanges = 2; // a pair should be present on at least two exchanges or more
+
+if ($ids) {
+
+    // load all markets from all exchanges
+    foreach ($ids as $id) {
+
+        // instantiate the exchange by id
+        $exchange = '\\ccxt\\' . $id;
+        $exchange = new $exchange ();
+
+        // save it in an assoc array for later use
+        $exchanges[$id] = $exchange;
+
+        $current_proxy = 0;
+
+        for ($num_retries = 0; $num_retries < $max_retries; $num_retries++) {
+
+            try {
+
+                $exchange->proxy = $proxies[$current_proxy];
+                $current_proxy = (++$current_proxy) % count ($proxies);
+
+                // load all markets from the exchange
+                $markets = $exchange->load_markets ();
+
+                // output a list of all market symbols
+                dump (green ($id), 'has', yellow (count ($exchange->symbols)), 'symbols');
+
+                break;
+
+            } catch (\ccxt\RequestTimeout $e) {
+                print_r ($e);
+            } catch (\ccxt\DDoSProtection $e) {
+                print_r ($e);
+            } catch (\ccxt\AuthenticationError $e) {
+                print_r ($e);
+            } catch (\ccxt\ExchangeNotAvailable $e) {
+                print_r ($e);
+            } catch (\ccxt\NotSupported $e) {
+                print_r ($e);
+            } catch (\ccxt\NetworkError $e) {
+                print_r ($e);
+            } catch (\ccxt\ExchangeError $e) {
+                print_r ($e);
+            } catch (Exception $e) {
+                print_r ($e);
+            }
+
+        }
+    }
+
+    dump (green ('Loaded all markets'));
+
+    $all_symbols = flatten (array_values (array_map (function ($exchange) {
+        return $exchange->symbols;
+    }, $exchanges)));
+
+    $unique_symbols = array_unique ($all_symbols);
+
+    // filter unique symbols leaving those present on at least 2 exchanges or more
+    $arbitrable_symbols = array_filter ($unique_symbols, function ($symbol) use (&$exchanges, $min_exchanges) {
+
+        $num_related_exchanges = count (array_filter ($exchanges, function ($exchange) use (&$symbol, $min_exchanges) {
+            return in_array ($symbol, $exchange->symbols);
+        }));
+
+        return ($num_related_exchanges >= $min_exchanges);
+    });
+
+    sort ($arbitrable_symbols);
+
+    $pairs = array_map (function ($symbol) use (&$exchanges) {
+        $result = array ('symbol' => $symbol);
+        foreach ($exchanges as $exchange) {
+            $result[$exchange->id] = in_array ($symbol, $exchange->symbols) ? $exchange->id : '';
+        }
+        return $result;
+    }, $arbitrable_symbols);
+
+    // output a table of all markets
+    @dump (tabulate (array_keys ($pairs[0]), array_map ('pairs_table_helper', $pairs)));
+
+} else {
+
+    dump ('Usage: php -f', __FILE__,  green ('id'));
+    print_supported_exchanges ();
+
+}
+
+?> 
+```