Add simple parser example

examples/simple-parser.php

@@ -0,0 +1,43 @@
+<?php
+
+require __DIR__ . "/../vendor/autoload.php";
+
+use Amp\ByteStream\Parser;
+use Amp\Loop;
+
+Loop::run(function () {
+    // Defines a generator that yields integers (number of bytes to read), strings (delimiter to search for), or
+    // null (read any amount of bytes).
+    $generator = function (callable $printer): \Generator {
+        while (true) {
+            $buffer = yield "\n"; // Reads until a new-line character is found.
+            $buffer = trim($buffer);
+            $printer($buffer); // Use the received data.
+        }
+    };
+
+    // The user of Parser is responsible for creating the Generator object, allowing anything to be passed into the
+    // generator that may be required.
+    $parser = new Parser($generator(function (string $parsedData) {
+        static $i = 0;
+        printf("[%d] %s\n", $i++, $parsedData);
+    }));
+
+    $parser->write("This\nis\n");
+
+    Loop::delay(1000, function () use ($parser) {
+        $parser->write("an\nexample\nof\n");
+    });
+
+    Loop::delay(2000, function ()  use ($parser) {
+        $parser->write("a\nsimple\n");
+    });
+
+    Loop::delay(3000, function ()  use ($parser) {
+        $parser->write("incremental\nstream\nparser");
+    });
+
+    Loop::delay(4000, function () use ($parser) {
+        $parser->end(); // Marks the end of data.
+    });
+});