PHP is a language that is used on a web server (http server), not on a web client (browser). This means that in order to run PHP on your android device (and not just display a web page served from a web server hosted elsewhere, online), you need to install a web server on your device. Luckily there's a few apps which provide this functionality.

• Web Server PHP/MyAdmin/MySQL

• AWebServer ( Http Web Server A

• In the past, I've had success with the free Palapa Web Server which is essentially a web / mysql server which runs on Android, which will run your PHP scripts, and it will also work offline. But this one no longer exists.

  To use Palapa web server, install the app, and copy your PHP / HTML files onto your phone. By default, the Palapa Web server uses /sdcard/pws/www/, so if you put your files there, it should pick them up. Then, launch the app, click "Start server", and go to http://127.0.0.1:8080 with your web browser on your android device, and it should work. Other web server apps will work similarly.

Note that setting up PHPMyAdmin, (if you need that for managing databases) can be a bit tricky, as you will need to download the extra packages for it, if the app you're using does not bundle it.

UPDATE AS OF JUNE 2, 2021

Option #1 ( Using CLI-based apks)
BEST OPTION

1. Termux (Installation of PHP, MARIADB, PHPMYADMIN packages within termux)
2. Terminal Emulator
3. UserLand

Option #2 (Using GUI-based apks)

1. KSWEB
2. Servers Ultimate

Summary:

• The above-mentioned apks do not require rooted device.
• CLI-based apks are highly recommended because a user can use UPDATED version of PHP, Apache, and any other packages you want to install to. The KickWeb apk does support running .php files BUT ,unfortunately, it doesn't have the latest PHP VERSION. Using an outdated version of PHP makes some of your PHP code to throw errors or warnings etc.

Try something like this you don't an open connection yet nor do you have a reader to read a response. Now it is prefered to run a external connection on an AsyncTask then return the response to a main thread. Set the response to be viewed as a EditText or an alert dialog so you can see any errors the server may be giving you also.

 URL url = "http://my.site.php?data=hello"
 HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setRequestMethod("GET");

        String line;
        StringBuilder sb= new StringBuilder();
        BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream(), "UTF-8"));
        while ((line=br.readLine()) != null) {
            sb.append(line);
            response =sb.toString();
        }
        br.close();
    } catch (Exception e) {
        e.printStackTrace();
    }

    return response;

You almost certainly don't want to run PHP on your Android. But in case you do, then you would want http://code.google.com/p/php-for-android/. Better link: http://phpforandroid.net/

There are several options i found:

1. http://phpforandroid.net/
2. http://www.talkandroid.com/6211-php-for-android-install-it-and-start-testing/

Please note that i have not used these frameworks and have no idea how good they are.

Another option is develope in java and make HTTP calls to the php in certain occasions when needed.

One more option, is phonegap which allows you to develope android application using HTML,Javascript,CSS but that will require some changes to your existing application.

Finally - someone has released the full package!

Bit Web Server (AMP; also see their homepage) stack running on Android. No hacking required. $2 to pay though!

If you are looking for a stack for iOS then the cydia-ios-lighttpd-php-mysql-web-stack does the trick: Should run lighttpd + php 5.4 + mysql - unfortunately only on jailbroken devices.

Edit: In case anyone is interested I have switched to Windows 8 tablet which happily runs all of the opensource AMP stacks. Runs very nicely and with a bit of Bootstrap styling I have a full feature sales order "app" for nothing. Little bit of code to sync back to the online version - no need to spend $50 per month per user on HandShake or similar.