Fix PHP 5.3 incompatibilities

CONTRIBUTING.md

@@ -1,4 +1,10 @@
 Contributing to the LaunchDarkly SDK for PHP
 ================================================
 
-We encourage pull-requests and other contributions from the community. We've also published an [SDK contributor's guide](http://docs.launchdarkly.com/v1.0/docs/sdk-contributors-guide) that provides a detailed explanation of how our SDKs work.
+We encourage pull-requests and other contributions from the community. We've also published an [SDK contributor's guide](http://docs.launchdarkly.com/v1.0/docs/sdk-contributors-guide) that provides a detailed explanation of how our SDKs work.
+
+
+This can help with getting php 5.3 on your mac: https://github.com/Homebrew/homebrew-php
+
+To see composer dependency graph: 
+`php composer.phar show -i -t`

circle.yml

@@ -1,7 +1,10 @@
 machine:
   php:
-    version: 5.4.37
+    version: 5.3.25
 
 test:
   override:
+    # syntax check php files
+    - find ./src -name "*.php" -type f -print0 | xargs -0 -I {} php -l {}
+    - find ./tests -name "*.php" -type f -print0 | xargs -0 -I {} php -l {}
     - vendor/bin/phpunit tests

composer.json

@@ -20,9 +20,10 @@
         }
     ],
     "require": {
-        "php": ">=5.3",
+        "php": "~5.3",
         "guzzle/guzzle": "dev-master#ecb935d2d0ecd8cddae4dcfb90515cac5e2cb023",
-        "psr/log": "1.0.0"
+        "psr/log": "1.0.0",
+        "justinrainbow/json-schema": "v1.6.0"
     },
     "require-dev": {
         "phpunit/phpunit": "4.8.26",