Introduce safe preg_split

Removes the need for extra assertions which makes the code
more readable, and reduces the overhead of an is_array check.

tests/unit/PregSplitTest.php

@@ -0,0 +1,48 @@
+<?php
+
+declare(strict_types=1);
+
+namespace phpDocumentor\Reflection;
+
+use phpDocumentor\Reflection\Exception\PcreException;
+use PHPUnit\Framework\TestCase;
+use function set_error_handler;
+use const E_WARNING;
+
+final class PregSplitTest extends TestCase
+{
+    /** @var callable|null */
+    private $errorHandler = null;
+
+    protected function tearDown() : void
+    {
+        if ($this->errorHandler === null) {
+            return;
+        }
+
+        set_error_handler($this->errorHandler, E_WARNING);
+    }
+
+    /**
+     * @covers \phpDocumentor\Reflection\Utils::pregSplit
+     */
+    public function testSimplePregSplit() : void
+    {
+        $result = Utils::pregSplit('/\s/', 'word split');
+
+        $this->assertSame(['word', 'split'], $result);
+    }
+
+    /**
+     * @covers \phpDocumentor\Reflection\Utils::pregSplit
+     */
+    public function testPregSplitThrowsOnError() : void
+    {
+        //We need to disable the error handler for phpunit... because we expect some errors here
+        $this->errorHandler = set_error_handler(static function () : void {
+        }, E_WARNING);
+
+        $this->expectException(PcreException::class);
+        Utils::pregSplit('~InvalidRegular)Expression~', 'some word');
+    }
+}