fix: allow to parse null or empty header element (#560)

* fix: allow to parse null or empty header element

* fix: change return null by ElementNull

* feat: add unit test for issue557 pdf file

* fix: make empty array for empty headers

* fix: PHP CS files fix

* fix: remove empty() to replace it by raw comparison

Co-authored-by: Konrad Abicht <hi@inspirito.de>

* removed obsolete )

Co-authored-by: Enzo <e.thibert@gda.fr>
Co-authored-by: Konrad Abicht <hi@inspirito.de>

src/Smalot/PdfParser/Parser.php

@@ -262,6 +262,11 @@ protected function parseHeader(array $structure, ?Document $document): Header
      */
     protected function parseHeaderElement(?string $type, $value, ?Document $document)
     {
+        $valueIsEmpty = null == $value || '' == $value || false == $value;
+        if (('<<' === $type || '>>' === $type) && $valueIsEmpty) {
+            $value = [];
+        }
+
         switch ($type) {
             case '<<':
             case '>>':

tests/Integration/ParserTest.php

@@ -270,6 +270,30 @@ public function testIssue391(): void
         );
     }
 
+    /**
+     * Tests if a PDF with null or empty string headers trigger an Exception.
+     *
+     * It happened because there was a check missing in Parser.php (parseHeaderElement function).
+     *
+     * @see https://github.com/smalot/pdfparser/issues/557
+     */
+    public function testIssue557(): void
+    {
+        /**
+         * PDF provided by @DogLoc for usage in our test environment.
+         *
+         * @see https://github.com/smalot/pdfparser/pull/560#issue-1461437944
+         */
+        $filename = $this->rootDir.'/samples/bugs/Issue557.pdf';
+
+        $document = $this->fixture->parseFile($filename);
+
+        $this->assertStringContainsString(
+            'Metal Face Inductive Sensor',
+            $document->getText()
+        );
+    }
+
     /**
      * Tests behavior when changing default font space limit (-50).
      *