I would like to have some sample PHP code which can be used to invoke Workflow to match Event Catalog which configures in SMGR. I can use POSTMAN in Chrome to post them but don't know how to code PHP for this to work.

My Event Catalog have following
Family = Demo
Type = HTTP Request
Version = 1
Schema Name = http_request
Schema Type = JSON
Schema = {title:emailVideoStartOutputSchema,type:object,properties:
{
emailRecipient:{type:string},
emailSubject:{type:string},
emailBody:{type:string},
emailSender:{type:string},
videoSubject:{type:string},
videoDescription:{type:string},
videoDurationDays:{type:string},
videoDurationHours:{type:string},
videoDurationMinutes:{type:string},
videoMaxParticipants:{type:string},
videoModeratorPin:{type:string},
videoParticipantPin:{type:string},
videoStartYear:{type:string},
videoStartMonth:{type:string},
videoStartDate:{type:string},
videoStartHour:{type:string},
videoStartMinute:{type:string}
}
}

You will have to use curl extension. Same samples here:
http://stackoverflow.com/questions/9802788/call-a-rest-api-in-php