diff --git a/core/lib/Drupal/Core/Serialization/JsonDecode.php b/core/lib/Drupal/Core/Serialization/JsonDecode.php
new file mode 100644
index 0000000000..14179ea24c
--- /dev/null
+++ b/core/lib/Drupal/Core/Serialization/JsonDecode.php
@@ -0,0 +1,80 @@
+<?php
+
+namespace Drupal\Core\Serialization;
+
+use Drupal\Core\Site\Settings;
+use Symfony\Component\Serializer\Encoder\JsonDecode as SymfonyJsonDecode;
+
+/**
+ * Provides a JsonDecode serialization implementation.
+ *
+ * This is a bridge between the Symfony 3 implementation which accepts two
+ * arguments for the constructor, and the Symfony 4.2 implementation which
+ * accepts an array. The only change is not triggering a deprecation notice
+ * for either format, and ensuring both the Symfony 3 and 4 properties are
+ * set by the constructor.
+ */
+class JsonDecode extends SymfonyJsonDecode {
+
+  /**
+   * True to return the result as an associative array, false for a nested stdClass hierarchy.
+   */
+  const ASSOCIATIVE = 'json_decode_associative';
+
+  const OPTIONS = 'json_decode_options';
+
+  /**
+   * Specifies the recursion depth.
+   */
+  const RECURSION_DEPTH = 'json_decode_recursion_depth';
+
+  protected $associative;
+  protected $recursionDepth;
+
+	protected $defaultContext =  [
+		self::ASSOCIATIVE => false,
+		self::OPTIONS => 0,
+		self::RECURSION_DEPTH => 512,
+	];
+
+	/**
+	 * Constructs a new JsonDecode instance.
+	 *
+	 * @param array $defaultContext
+	 */
+	public function __construct($defaultContext = [], int $depth = 512)
+	{
+		if (!\is_array($defaultContext)) {
+			$defaultContext = [
+				self::ASSOCIATIVE => (bool) $defaultContext,
+				self::RECURSION_DEPTH => $depth,
+			];
+      $this->associative = $defaultContext;
+      $this->recursionDepth = (int) $depth;
+		}
+    else {
+      $this->associative = isset($defaultContext[self::ASSOCIATIVE]) ? (bool) $defaultContext[self::ASSOCIATIVE] : FALSE;
+      $this->recursionDepth = isset($defaultContext[self::RECURSION_DEPTH]) ? (int)  $defaultContext[self::RECURSION_DEPTH] : 512;
+    }
+
+		$this->defaultContext = array_merge($this->defaultContext, $defaultContext);
+	}
+
+  /**
+   * {@inheritdoc}
+   */
+	public function decode($data, $format, array $context = array()) {
+    $associative = isset($context[self::ASSOCIATIVE]) ? $context[self::ASSOCIATIVE] : $this->defaultContext[self::ASSOCIATIVE];
+    $recursionDepth = isset($context[self::RECURSION_DEPTH]) ? $context[self::RECURSION_DEPTH] : $this->defaultContext[self::RECURSION_DEPTH];
+    $options = isset($context[self::OPTIONS]) ? $context[self::OPTIONS] : $this->defaultContext[self::OPTIONS];
+
+    $decodedData = json_decode($data, $associative, $recursionDepth, $options);
+
+    if (JSON_ERROR_NONE !== json_last_error()) {
+      throw new NotEncodableValueException(json_last_error_msg());
+    }
+
+    return $decodedData;
+	}
+
+}
diff --git a/core/lib/Drupal/Core/Serialization/JsonEncode.php b/core/lib/Drupal/Core/Serialization/JsonEncode.php
new file mode 100644
index 0000000000..ab4c38049c
--- /dev/null
+++ b/core/lib/Drupal/Core/Serialization/JsonEncode.php
@@ -0,0 +1,58 @@
+<?php
+
+namespace Drupal\Core\Serialization;
+
+use Drupal\Core\Site\Settings;
+use Symfony\Component\Serializer\Encoder\JsonEncode as SymfonyJsonEncode;
+
+/**
+ * Provides a JsonEncode serialization implementation.
+ *
+ * This is a bridge between the Symfony 3 implementation which only accepts an
+ * int for the constructor, and the Symfony 4.2 implementation which accepts an
+ * array and deprecates int. The only change is not triggering a deprecation
+ * notice for either format, and ensuring both the Symfony 3 and 4 properties
+ * are set by the constructor.
+ */
+class JsonEncode extends SymfonyJsonEncode {
+
+  const OPTIONS = 'json_encode_options';
+
+  protected $defaultContext = [
+    self::OPTIONS => 0,
+  ];
+
+  protected $options;
+
+  /**
+   * @param array $defaultContext
+   */
+  public function __construct($defaultContext = []) {
+    if (!\is_array($defaultContext)) {
+      $this->defaultContext[self::OPTIONS] = (int) $defaultContext;
+      $this->options = $defaultContext;
+    }
+    else {
+      $this->options = $defaultContext[self::OPTIONS];
+      $this->defaultContext = array_merge($this->defaultContext, $defaultContext);
+    }
+  }
+
+	/**
+	 * Encodes PHP data to a JSON string.
+	 *
+	 * {@inheritdoc}
+	 */
+	public function encode($data, $format, array $context = []) {
+			$jsonEncodeOptions = isset($context[self::OPTIONS]) ? $context[self::OPTIONS] : $this->defaultContext[self::OPTIONS];
+			$encodedJson = json_encode($data, $jsonEncodeOptions);
+
+			if (JSON_ERROR_NONE !== json_last_error() && (false === $encodedJson || !($jsonEncodeOptions & JSON_PARTIAL_OUTPUT_ON_ERROR))) {
+					throw new NotEncodableValueException(json_last_error_msg());
+			}
+
+			return $encodedJson;
+	}
+
+
+}
diff --git a/core/modules/serialization/src/Encoder/JsonEncoder.php b/core/modules/serialization/src/Encoder/JsonEncoder.php
index 964c2951f6..9a018bce75 100644
--- a/core/modules/serialization/src/Encoder/JsonEncoder.php
+++ b/core/modules/serialization/src/Encoder/JsonEncoder.php
@@ -4,9 +4,9 @@
 
 use Symfony\Component\Serializer\Encoder\DecoderInterface;
 use Symfony\Component\Serializer\Encoder\EncoderInterface;
-use Symfony\Component\Serializer\Encoder\JsonDecode;
-use Symfony\Component\Serializer\Encoder\JsonEncode;
 use Symfony\Component\Serializer\Encoder\JsonEncoder as BaseJsonEncoder;
+use Drupal\Core\Serialization\JsonDecode;
+use Drupal\Core\Serialization\JsonEncode;
 
 /**
  * Adds 'ajax to the supported content types of the JSON encoder'
@@ -31,9 +31,9 @@ public function __construct(JsonEncode $encodingImpl = NULL, JsonDecode $decodin
     // Encode <, >, ', &, and " for RFC4627-compliant JSON, which may also be
     // embedded into HTML.
     // @see \Symfony\Component\HttpFoundation\JsonResponse
-    $json_encoding_options = JSON_HEX_TAG | JSON_HEX_APOS | JSON_HEX_AMP | JSON_HEX_QUOT;
+    $json_encoding_options = [JsonEncode::OPTIONS => JSON_HEX_TAG | JSON_HEX_APOS | JSON_HEX_AMP | JSON_HEX_QUOT];
     $this->encodingImpl = $encodingImpl ?: new JsonEncode($json_encoding_options);
-    $this->decodingImpl = $decodingImpl ?: new JsonDecode(TRUE);
+    $this->decodingImpl = $decodingImpl ?: new JsonDecode([JsonDecode::ASSOCIATIVE => true]);
   }
 
   /**
diff --git a/core/tests/Drupal/Tests/ComposerIntegrationTest.php b/core/tests/Drupal/Tests/ComposerIntegrationTest.php
index 2d34dcb74c..59ff791295 100644
--- a/core/tests/Drupal/Tests/ComposerIntegrationTest.php
+++ b/core/tests/Drupal/Tests/ComposerIntegrationTest.php
@@ -18,7 +18,7 @@ class ComposerIntegrationTest extends UnitTestCase {
    *
    * @todo Remove as part of https://www.drupal.org/node/2908079
    */
-  const MIN_PHP_VERSION = '5.5.9';
+  const MIN_PHP_VERSION = '7.1.3';
 
   /**
    * Gets human-readable JSON error messages.