Asynchronous Function Call in PHP

Question

I am working on an a PHP web application and i need to perform some network operations in the request like fetching someone from remote server based on user s request   Is it possible to simulate asynchronous behavior in PHP given that i have to pass some data to a function and also need output from it   My code is like    lt  php        data1   processGETandPOST          data2   processGETandPOST          data3   processGETandPOST           response1   makeNetworkCall  data1         response2   makeNetworkCall  data2         response3   makeNetworkCall  data3         processNetworkResponse  response1        processNetworkResponse  response2        processNetworkResponse  response3           HTML and OTHER UI STUFF HERE         exit    gt    Each network operation takes around 5 seconds to complete adding a total of 15 seconds to the response time of my application given i make 3 requests   The  makeNetworkCall   function just do a HTTP POST request   The remote server is an 3rd party API so i don t have any control over there   PS  Please do not answer giving suggestions about AJAX or Other things  I am currently looking if i can do this through PHP may be with an C   extension or something like that

User · Answer

cURL is going to be your only real choice here (either that, or using non-blocking sockets and some custom logic).

This link should send you in the right direction. There is no asynchronous processing in PHP, but if you're trying to make multiple simultaneous web requests, cURL multi will take care of that for you.

User · Answer

I think some code about the cURL solution is needed here  so I will share mine  it was written mixing several sources as the PHP Manual and comments    It does some parallel HTTP requests  domains in  aURLs  and print the responses once each one is completed  and stored them in  done for other possible uses    The code is longer than needed because the realtime print part and the excess of comments  but feel free to edit the answer to improve it    lt  php    Strategies to avoid output buffering  ignore the block if you don t want to print the responses before every cURL is completed    ini set  output buffering    off       Turn off output buffering ini set  zlib output compression   false      Turn off PHP output compression          Flush  send  the output buffer and turn off output buffering ob end flush    while   ob end flush             apache setenv  no-gzip   true     prevent apache from buffering it for deflate gzip ini set  zlib output compression   false   header  Content-type  text plain      Remove to use HTML ini set  implicit flush   true      Implicitly flush the buffer s  ob implicit flush true   header  Cache-Control  no-cache       recommended to prevent caching of event data   string     for  i 0  i lt 1000    i   string        output  string     Safari and Internet Explorer have an internal 1K buffer    Here starts the program output  function output  string       ob start        echo  string      if ob get level   gt 0  ob flush        ob end clean        clears buffer and closes buffering     flush       function multiprint  aCurlHandles  print true       global  done         iterate through the handles and get your content     foreach  aCurlHandles as  url  gt  ch           if  isset  done  url       only check for unready responses              html   curl multi getcontent  ch     get the content                        if  html                    done  url   html                  if  print  output   html  PHP EOL                                                function full curl multi exec  mh   amp  still running        do          rv   curl multi exec  mh   still running     execute the handles        while   rv    CURLM CALL MULTI PERFORM     CURLM CALL MULTI PERFORM means you should call curl multi exec   again because there is still data available for processing     return  rv      set time limit 60     Max execution time 1 minute   aURLs   array  http   domain script1 php   http   domain script2 php        array of URLs   done array       Responses of each URL        Initialization      aCurlHandles   array       create an array for the individual curl handles      mh   curl multi init       init the curl Multi and returns a new cURL multi handle     foreach   aURLs as  id  gt  url      add the handles for each url                  ch   curl init       init curl  and then setup your options         curl setopt  ch  CURLOPT URL   url           curl setopt  ch  CURLOPT RETURNTRANSFER 1      returns the result - very important         curl setopt  ch  CURLOPT HEADER  0      no headers in the output          aCurlHandles  url     ch          curl multi add handle  mh  ch                Process      active   null    the number of individual handles it is currently working with      mrc full curl multi exec  mh   active          As long as there are active connections and everything looks OK        while  active  amp  amp   mrc    CURLM OK      CURLM OK means is that there is more data available  but it hasn t arrived yet               Wait for activity on any curl-connection and if the network socket has some data            if  descriptions curl multi select  mh 1     -1     If waiting for activity on any curl multi connection has no failures  1 second timeout                   usleep 500     Adjust this wait to your needs                              Process the data for as long as the system tells us to keep getting it              mrc full curl multi exec  mh   active                         output  Still active processes   active  PHP EOL                         Printing each response once it is ready             multiprint  aCurlHandles                            Printing all the responses at the end       multiprint  aCurlHandles false                Finalize     foreach   aCurlHandles as  url  gt  ch            curl multi remove handle  mh   ch      remove the handle  assuming  you are done with it             curl multi close  mh      close the curl multi handler   gt

User · Answer

This old question has a new answer  There are a few  quot async quot  solutions for PHP this days  which are equivalent to Python s multiprocess in the sense that they spawn new independent PHP processes rather than manage it at the framework level  The two solutions I have seen are  Quick and easy  https   github com spatie async Big tank with concurrency management  https   github com amphp amp  Give them a try

User · Answer

One way is to use pcntl fork   in a recursive function   function networkCall       data   processGETandPOST       response   makeNetworkCall  data     processNetworkResponse  response     return true     function runAsync  times      pid   pcntl fork      if   pid    -1        die  could not fork        else if   pid           we are the parent      times -  1      if  times gt 0        runAsync  times       pcntl wait  status     Protect against Zombie children     else          we are the child     networkCall        posix kill getmypid    SIGKILL          runAsync 3     One thing about pcntl fork   is that when running the script by way of Apache  it doesn t work  it s not supported by Apache   So  one way to resolve that issue is to run the script using the php cli  like  exec  php fork php   output   from another file  To do this you ll have two files  one that s loaded by Apache and one that s run with exec   from inside the file loaded by Apache like this   apacheLoadedFile php  exec  php fork php   output     fork php  function networkCall       data   processGETandPOST       response   makeNetworkCall  data     processNetworkResponse  response     return true     function runAsync  times      pid   pcntl fork      if   pid    -1        die  could not fork        else if   pid           we are the parent      times -  1      if  times gt 0        runAsync  times       pcntl wait  status     Protect against Zombie children     else          we are the child     networkCall        posix kill getmypid    SIGKILL          runAsync 3

User · Answer

There is also http v2 which is a wrapper for curl  Can be installed via pecl    http   devel-m6w6 rhcloud com mdref http

User · Answer

I think if the HTML and other UI stuff needs the data returned then there is not going to be a way to async it    I believe the only way to do this in PHP would be to log a request in a database and have a cron check every minute  or use something like Gearman queue processing  or maybe exec   a command line process  In the meantime you php page would have to generate some html or js that makes it reload every few seconds to check on progress  not ideal   To sidestep the issue  how many different requests are you expecting  Could you download them all automatically every hour or so and save to a database

User · Answer

I dont have a direct answer  but you might want to look into these things    Recoil project - https   github com recoilphp recoil php s LibEvent extension  http   www php net manual en book libevent php process forking http   www php net manual en function pcntl-fork php message brokers  i e  you could start workers to make the HTTP calls and once that job is done  insert a new job describing the work that needs to be done in order to process the cached HTTP response body

User · Answer

Nowadays  it s better to use queues than threads  for those who don t use Laravel there are tons of other implementations out there like this    The basic idea is  your original PHP script puts tasks or jobs into a queue  Then you have queue job workers running elsewhere  taking jobs out of the queue and starts processing them independently of the original PHP   The advantages are    Scalability - you can just add worker nodes to keep up with demand  In this way  tasks are run in parallel  Reliability - modern queue managers such as RabbitMQ  ZeroMQ  Redis  etc  are made to be extremely reliable

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