PHP to receive any POST request, and write it to file on the server.

receive_post_data.php

<?php
    
    /*

        #### Tested using PHP 7 under Apache.


        A script to capture a json POST request, and print it
        (nearly*) as is to an output text file. Outputs are
        written to a subfolder `outputs` (make sure this folder
        exists), separated into one file per day.
        
        This is intended for use in reverse-engineering POST
        requests. Since it will accept and write anything, I
        wouldn't recommend using it in production.

        * We add a server-side timestamp to each entry.


        2 options are provided, uncomment one option as needed.


        OPTION 1 prints one line per request, in a json format.
        eg:
        {"2000-01-01 12:00:00":{"param1":"val1","param2","val2"}}
        

        OPTION 2 prints one line per parameter, indented to group
        each request. eg:
        server.time: 2000-01-01 12:00:00:
            param1: val1
            param2: val2

    */



    # parse server-side timestamps
    $now = date( 'Y-m-d H:i:s' );
    $today = date( 'Ymd' );



    ### OPTION 1 START ###

    # specify the output file, separating by date
    $file = "outputs/" . $today . ".js";

    # construct a complete line for the output file
    $string = '{"' . $now . '":' . json_encode( $_POST ) . "}\n";

    # print the contructed line to the output file
    file_put_contents( $file, $string, FILE_APPEND );

    ### OPTION 1 END ###



    /*
    
    ### OPTION 2 START ###

    # specify the output file, separating by date
    $file = "outputs/" . $today . ".txt";

    # write a timestamp line
    file_put_contents(  $file,
                        "server.time: $now:\n",
                        FILE_APPEND );

    # write an indented line for each parameter
    foreach ($_POST as $param_name => $param_val) {
        file_put_contents(  $file,
                            "    $param_name: $param_val\n",
                            FILE_APPEND );
    };

    ### OPTION 2 END ###

    */



    # respond to the sender
    header( "HTTP/1.1 200" );

?>