@Adeyeye George The doc link mentioned seems to point to the bing image search API which uses text in the query string to get the results. Bing visual search along with other bing search API's migrated to bing from cognitive services and the appropriate doc link for all services is the following.
I am not an expert on PHP but the following SO thread could help to perform a PHP visual search operation. I hope this helps.
P.S: SO thread referenced
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