If you're talking about using a server backend to deliver content from PHP to a user client written in HTML/Javascript, this is very easy to do using iOS. You can use UIWebKit to display HTML and execute Javascript code. If you want cross-language support between Obj-C and JS, Objective-C can talk to Javascript using:
[UIWebView stringByEvaluatingJavaScriptFromString:(NSString *)];
for Javascript talking to Objective C, this can be accomplished using delegates (specifically UIWebViewDelegate) which is detailed here.