Error Testing Azure CDN

I’ve been trying to hook our web site (hosted in Azure as a CentOS 7 VM) up to the CDN we have configured in Azure (which just involves uploading to a blob container). When I key in the details and press the “Test Microsoft Azure Storage Upload” button it fails. I see the following error in Apache’s error log:

[Wed Aug 23 04:51:18.108322 2017] [:error] [pid 23677] [client 192.168.10.119:63727] PHP Parse error: syntax error, unexpected ‘$sendAsync’ (T_VARIABLE) in /www/wp/wp-content/plugins/w3-total-cache/lib/Azure/MicrosoftAzureStorage/Common/Internal/ServiceRestProxy.php on line 220, referer: …/wp-admin/admin.php?page=w3tc_cdn

I’m not able to find any errors elsewhere. We’re running W3 Total Cache 0.9.5.4 on WordPress 4.8.1 on PHP 5.4.16 on Apache 2.4.6 on CentOS 7.3.1611.