How To Create A PHP Daemon (Simple Examples)

Welcome to a quick tutorial and example of how to create a PHP daemon. Need to run a “service” PHP script in the background? Send out emails, fetch updates, or monitor something?

Yes, it’s that simple. Let us walk through a few more examples in this guide – Read on!

ⓘ I have included a zip file with all the example source code at the start of this tutorial, so you don’t have to copy-paste everything… Or if you just want to dive straight in.

 

 

TABLE OF CONTENTS

Download & Notes	Simple Daemon	Useful Bits & Links
The End

 

 

QUICK NOTES

If you spot a bug, feel free to comment below. I try to answer short questions too, but it is one person versus the entire world… If you need answers urgently, please check out my list of websites to get help with programming.

 

EXAMPLE CODE DOWNLOAD

Click here to download the source code, I have released it under the MIT license, so feel free to build on top of it or use it in your own project.

 

 

 

EXAMPLE 1) BASIC MECHANICS

<?php
// (A) COMMAND LINE ONLY!
if (isset($_SERVER["REMOTE_ADDR"]) || isset($_SERVER["HTTP_USER_AGENT"]) || !isset($_SERVER["argv"])) {
  exit("Please run this script from command line");
}

// (B) SETTINGS
$cycle = 10; // WAIT 10 SECS BETWEEN CYCLES
 
// (C) RUN
while (true) {
  echo "It works!" . PHP_EOL;
  sleep($cycle);
}

Yep, that’s all for the “basics” of a “daemon” in PHP. Just run this script in the command line PHP 1-basic.php, and it will output It works! every 10 seconds… Not very useful, so let’s go through more practical examples below.

 

 

EXAMPLE 2) FETCH DATA FROM API

<?php
// (A) COMMAND LINE ONLY!
if (isset($_SERVER["REMOTE_ADDR"]) || isset($_SERVER["HTTP_USER_AGENT"]) || !isset($_SERVER["argv"])) {
  exit("Please run this script from command line");
}

// (B) SETTINGS
$cycle = 10; // WAIT 10 SECS BETWEEN CYCLES
$url = "http://localhost/2b-dummy.txt"; // DUMMY SERVER

// (C) RUN
while (true) {
  // (C1) CURL INIT
  $ch = curl_init();
  curl_setopt($ch, CURLOPT_URL, $url);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
 
  // (C2) FETCH UPDATES FROM DUMMY SERVER
  $result = curl_exec($ch);
  if (curl_errno($ch)) { echo curl_error($ch) . PHP_EOL; }
  else { echo $result . PHP_EOL; }
  curl_close($ch);
 
  // (C3) UPDATE DATABASE
  $result = json_decode($result, true);
  // $sql = "UPDATE `rates` SET `EUR` = ?";
  // $sql = "UPDATE `rates` SET `GBP` = ?";
  unset($result);
 
  // (C4) WAIT FOR NEXT CYCLE
  sleep($cycle);
}

{"EUR":1.17,"GBP":1.38}

Let’s say that we have an e-commerce or trading website that deals with multiple currencies. So in this one, we periodically:

• Use CURL to fetch the latest exchange rate for EUR-USD and GBP-USD.
• Then update the rates in the local database.

 

 

EXAMPLE 3) MONITOR SERVER

<?php
// (A) COMMAND LINE ONLY!
if (isset($_SERVER["REMOTE_ADDR"]) || isset($_SERVER["HTTP_USER_AGENT"]) || !isset($_SERVER["argv"])) {
  exit("Please run this script from command line");
}
 
// (B) SETTINGS
$url = "http://localhost";
$log = "stats.txt";
$cycle = 10; // WAIT 10 SECS BETWEEN CYCLES
 
// (C) INIT LOG FILE
file_put_contents($log, "");
 
// (D) RUN MONITOR
while (true) {
  // (D1) CURL TEST FETCH
  $ch = curl_init();
  curl_setopt($ch, CURLOPT_URL, $url);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
  $result = curl_exec($ch);

  // (D2) ERROR
  if (curl_errno($ch)) {
    $line = sprintf("%s %s\r\n",
      date("Y-m-d H:i:s"), curl_error($ch)
    );
  }

  // (D3) OK
  else {
    $info = curl_getinfo($ch);
    $line = sprintf("%s %s\r\n",
      date("Y-m-d H:i:s"), $info["http_code"], $info["total_time_us"]
    );
  }
  curl_close($ch);
 
  // (D4) RECORD
  file_put_contents($log, $line, FILE_APPEND);
 
  // (D5) NEXT CYCLE
  sleep($cycle);
}

Need to monitor the performance or uptime of a server? Use this script… Although a text file is not the best, recording the stats in a database will be a better idea.

 

 

 

LIMITATIONS

As you may have already guessed, this method will permanently take up one process thread. While some people may flip out at the idea of an infinite loop, but it works – It is at least good for the people who don’t have access to install a PHP extension on the server. Most importantly, it is very easy to implement.

 

RUN AT STARTUP

It will be a pain to manually run the script every time, so here is how we schedule it to run at startup instead:

 

LINKS & REFERENCES

• PHP Daemon with pcntl extension
• PHP Daemon on GitHub
• Run PHP Script In Background – Code Boxx
• Schedule PHP Script – Code Boxx

 

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