2 files changed, 116 insertions, 2 deletions

diff --git a/src/Writer.php b/src/Writer.php
index 41c5609..9318f23 100644
--- a/src/Writer.php
+++ b/src/Writer.php
@@ -32,8 +32,9 @@
 */
 namespace League\Csv;
 
-use InvalidArgumentException;
 use Traversable;
+use InvalidArgumentException;
+use OutOfBoundsException;
 
 /**
  *  A class to manage data insertion into a CSV
@@ -44,6 +45,15 @@ use Traversable;
  */
 class Writer extends AbstractCsv
 {
+
+    const NULL_AS_EXCEPTION = 1;
+
+    const NULL_AS_SKIP_CELL = 2;
+
+    const NULL_AS_EMPTY = 3;
+
+    private $null_handling = self::NULL_AS_EXCEPTION;
+
     /**
      * The constructor
      *
@@ -56,6 +66,62 @@ class Writer extends AbstractCsv
     }
 
     /**
+     * Tell the class how to handle null value
+     *
+     * @param integer $value a Writer null behavior constant
+     *
+     * @return self
+     *
+     * @throws OutOfBoundsException If the Integer is not valid
+     */
+    public function setNullHandling($value)
+    {
+        if (!in_array($value, [self::NULL_AS_SKIP_CELL, self::NULL_AS_EXCEPTION, self::NULL_AS_EMPTY])) {
+            throw new OutOfBoundsException(
+                'invalid value for null behavior'
+            );
+        }
+        $this->null_handling = $value;
+
+        return $this;
+    }
+
+    /**
+     * null handling getter
+     *
+     * @return integer
+     */
+    public function getNullHandling()
+    {
+        return $this->null_handling;
+    }
+
+    /**
+     * Format the row according to the null handling behavior
+     *
+     * @param array $row
+     *
+     * @return array
+     */
+    private function formatRow(array $row)
+    {
+        if (self::NULL_AS_EMPTY == $this->null_handling) {
+            foreach ($row as &$value) {
+                if (is_null($value)) {
+                    $value = '';
+                }
+            }
+            unset($value);
+
+            return $row;
+        }
+
+        return array_filter($row, function ($value) {
+            return ! is_null($value);
+        });
+    }
+
+    /**
      * Add a new CSV row to the generated CSV
      *
      * @param mixed $row a string, an array or an object implementing to '__toString' method
@@ -75,9 +141,11 @@ class Writer extends AbstractCsv
             );
         }
         $check = array_filter($row, function ($value) {
-            return self::isValidString($value);
+            return (is_null($value) && self::NULL_AS_EXCEPTION != $this->null_handling)
+            || self::isValidString($value);
         });
         if (count($check) == count($row)) {
+            $row = $this->formatRow($row);
             $this->csv->fputcsv($row, $this->delimiter, $this->enclosure);
 
             return $this;
diff --git a/test/WriterTest.php b/test/WriterTest.php
index e22cd9a..2e87c91 100644
--- a/test/WriterTest.php
+++ b/test/WriterTest.php
@@ -4,6 +4,7 @@ namespace League\Csv\Test;
 
 use SplTempFileObject;
 use ArrayIterator;
+use LimitIterator;
 use PHPUnit_Framework_TestCase;
 use DateTime;
 use League\Csv\Writer;
@@ -39,6 +40,51 @@ class WriterTest extends PHPUnit_Framework_TestCase
     }
 
     /**
+     * @expectedException OutOfBoundsException
+     */
+    public function testSetterGetterNullBehavior()
+    {
+        $this->csv->setNullHandling(Writer::NULL_AS_SKIP_CELL);
+        $this->assertSame(Writer::NULL_AS_SKIP_CELL, $this->csv->getNullHandling());
+
+        $this->csv->setNullHandling(23);
+    }
+
+    public function testInsertNullToSkipCell()
+    {
+        $expected = [
+            ['john', 'doe', 'john.doe@example.com'],
+            'john,doe,john.doe@example.com',
+            ['john', null, 'john.doe@example.com'],
+        ];
+        $this->csv->setNullHandling(Writer::NULL_AS_SKIP_CELL);
+        foreach ($expected as $row) {
+            $this->csv->insertOne($row);
+        }
+        $iterator = new LimitIterator($this->csv->getIterator(), 2, 1);
+        $iterator->rewind();
+        $res = $iterator->getInnerIterator()->current();
+        $this->assertSame(['john', 'john.doe@example.com'], $res);
+    }
+
+    public function testInsertNullToEmpty()
+    {
+        $expected = [
+            ['john', 'doe', 'john.doe@example.com'],
+            'john,doe,john.doe@example.com',
+            ['john', null, 'john.doe@example.com'],
+        ];
+        $this->csv->setNullHandling(Writer::NULL_AS_EMPTY);
+        foreach ($expected as $row) {
+            $this->csv->insertOne($row);
+        }
+        $iterator = new LimitIterator($this->csv->getIterator(), 2, 1);
+        $iterator->rewind();
+        $res = $iterator->getInnerIterator()->current();
+        $this->assertSame(['john', '', 'john.doe@example.com'], $res);
+    }
+
+    /**
      * @expectedException InvalidArgumentException
      */
     public function testFailedInsertWithWrongData()