PHP Warning: get_headers(): This function may only be used against URLs

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Setup

• SMW version: 3.1.6
• MW version: 1.31.6
• PHP version: 7.0.33-0ubuntu0.16.04.16
• DB system (MySQL, Blazegraph, etc.) and version: MySQL-5.7.32-0ubuntu0.16.04.1
• Elasticsearch version: 5.6.16

Issue

This issue came to light after having found the cause of #4488. In the ElasticSearch file ingestion process, a call is made to the get_headers() function in the FileHandler class (here) using a URL that is based on $wgServer.

According to the documentation of $wgServer, MediaWiki supports setting it to a protocol-relative URL (e.g., //www.mediawiki.org). Doing this however causes the previously mentioned call to get_header() to fail, since it is unable to recognize the given URL as a valid URL:

PHP Warning:  get_headers(): This function may only be used against URLs

This causes the get_headers() function to return false, which causes the file ingestion to fail. This should not happen, since a protocol-relative $wgServer should be allowed.

Steps to reproduce the observation:

• Set $wgServer to a protocol-relative URL (e.g. //www.mediawiki.org)
• Enable experimental.file.ingest for ElasticStore
• Run rebuildElasticIndex maintenance script

[kghbln]

Thanks for your elaborate report and your findings.