Fail to retrieve the value from gsm sim 900A by using AT Command to PHP script
I am not sure but, in this tutorial at page 8, it does almost the same code pattern like yours. You might want to check it. Sorry but I don't know PHP, I can't help you with it. 

But I am confused with AT+HTTPACTION, since AT+HTTPACTION=0 is the read and AT+HTTPACTION=1 is the post. Check the tutorial and optimize your commands.

Also check this one. It writes WAIT=6 after AT+HTTPREAD before terminating it.