Wrap file paths in double quotes to prevent issues in file paths cont…

…ain spaces

src/PdfStitcher.php

@@ -85,8 +85,8 @@ private function getShellCommand($filePath): string
             throw new RuntimeException('Ghostscript (`gs`) is not installed. Please install it.');
         }
 
-        $command = 'gs -q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile='.$filePath.' ';
-        $command .= implode(' ', $this->inputFiles);
+        $command = 'gs -q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile='.Utils::quote($filePath).' ';
+        $command .= implode(' ', array_map([Utils::class, 'quote'], $this->inputFiles));
 
         return $command;
     }

src/Utils.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace LangleyFoxall\PdfStitcher;
+
+/**
+ * Class Utils
+ * @package LangleyFoxall\PdfStitcher
+ */
+abstract class Utils
+{
+    /**
+     * Wraps a specified string in double quotes and returns it.
+     *
+     * @param string $string
+     * @return string
+     */
+    public static function quote(string $string)
+    {
+        return '"'.$string.'"';
+    }
+}