This is a simple step by step guide to creating a form that will capture data and store it in a mysql database on your server from within a wordpress post

Note: the below example is a live, working form on this page

Step 1:

Create a simple form for a petition, contact request, or registration:

Name:
Address:
City:
State:
Email:
Comment:
	Save

Here is the html code for it:

<table>
<tr><th>Name:</th><td><input id="userName" /></td></tr>
<tr><th>Address:</th><td> <input id="userAddress" /></td></tr>
<tr><th>City:</th><td> <input id="userCity" /></td></tr>
<tr><th>State:</th><td> <input id="userState> /></td></tr>
<tr><th>Zip:</th><td> <input id="userZip" /></td></tr>
<tr><th>Email:</th><td> <input id="userEmail" /></td></tr>
<tr><th>Comment:</th><td> <textarea id="userComment" ></textarea></td></tr>
<tr><th><td colspan=2><button type="button" onclick="saveUser();">Save</button></td></tr>
</table>

Step 2:

Create a javascript function to process the form and send it to the server. The following is a javascript function added to the page using the CSS & Javascript Toolbox plugin (it uses jquery because wordpress already has that available):

//Process the form and save the data record
function saveUser() {
  //First gather the form parameters and make sure name and email at least are populated
  var name = jQuery("#userName").val();
  var address = jQuery("#userAddress").val();
  var city = jQuery("#userCity").val();
  var state = jQuery("#userState").val();
  var zip = jQuery("#userZip").val();
  var email = jQuery("#userEmail").val();
  var comment = jQuery("#userComment").val();
  if (name.length<1 || email.length<1) {
    alert("Please at least enter your name and email.");
    return false;
  } else {
    //Now send the data to a server side function to really validate it and save it.
    jQuery.ajax({
      type: "POST",
      url: "/ajax/saveUser.php",
      data: { name:name,address:address,city:city,state:state,zip:zip,email:email,comment:comment }
    }).done(function( results ) {
      if(results.length<1){ // network error
        alert("There was a network error, please try again or contact support and tell them what you are trying to do.");
      } else { // this is a successful interaction
        var resultObj = jQuery.parseJSON(results);
                
        if (resultObj.errorMsg.length>0) {  
          alert(resultObj.errorMsg);
        } else {
    	  //Record save successful
          alert("Thanks for your information, it was saved successfully!");
          //Show the user what they have entered:
          jQuery("#userList").html(resultObj.userList);
        }
      }
    });
  }
}

Step 3:

Make sure you have a database table ready to store the information. Below is a simple table used to store the info in this example:

CREATE TABLE IF NOT EXISTS `user_info` (
  `userID` int(11) NOT NULL AUTO_INCREMENT,
  `userName` varchar(80) DEFAULT NULL,
  `address` varchar(100) DEFAULT NULL,
  `city` varchar(80) DEFAULT NULL,
  `state` varchar(40) DEFAULT NULL,
  `zip` varchar(5) DEFAULT NULL,
  `email` varchar(80) DEFAULT NULL,
  `comment` text DEFAULT NULL,
  `userIP` VARCHAR( 30 ) DEFAULT NULL,
  `dateAdded` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`userID`),
  KEY `userIP` (`userIP`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;

Step 4:

Create the server side code to accept the form data, really validate it, and put it in the database or send back an error. Here is the contents of a server side code which will do all that for the example data above. Since this form is “in the wild”, I’m capturing the IP address because I will only show results to people that they entered themselves:

/*
 * File: saveUser.php
 * Description: This file takes the passed in user information and validates it before
 * 	saving it to the database and returning content to show on the page. 
 * Inputs (in POST): 
 * 	userName, address, city, state, zip, email, comment
 * Outputs:
 * 	either an error or nothing
 */
include("db.php"); // define your database credentials in another file

#connect to the database
$db = mysqli_connect($servername, $username, $password, $dbname);
mysqli_select_db($db,$dbname) or die('Could not select database');

#Get the passed in parameters into local variables, escaped for database input
$userName = empty($_POST['userName'])?'':addslashes($_POST['userName']);
$address = empty($_POST['address'])?'':addslashes($_POST['address']);
$city = empty($_POST['city'])?'':addslashes($_POST['city']);
$state = empty($_POST['state'])?'':addslashes($_POST['state']);
//only accept 5 numbers for zip
$zip = empty($_POST['zip'])?'':substr(preg_replace('/\D/','',$_POST['zip']),0,5);
$email = empty($_POST['email'])?'':addslashes($_POST['email']);
$comment = empty($_POST['comment'])?'':addslashes($_POST['comment']);
$userIP = $_SERVER['REMOTE_ADDR'];

#This is an array used for gathering all the outputs of this file
$jsonObj = array();
$jsonObj['errorMsg'] = "";
$debug=false;

#Validate inputs
if (empty($userName) or empty($email)) {
	$jsonObj['errorMsg'] = "Please at least enter your name and email.";
} else if (strpos($email,'@')===false) {
	//there are many more validations that can be made for emails but this is a start
	$jsonObj['errorMsg'] = "Please enter a valid email.";
}

#Enter the data record
if (empty($jsonObj['errorMsg'])) {	
	$sql = "insert into user_info (userName,address,city,state,zip,email,comment,userIP) 
			values
			('".$userName."','".$address."','".$city."','".$state."','".$zip."','".$email."',
			'".$comment."','".$userIP."')";
	if ($debug) echo "about to run $sql ";
	mysqli_query($db, $sql); $err = mysqli_error($db); if (!empty($err)) $jsonObj['errorMsg'] = $err;
}

#Now get the list of data entered by this IP, without any script tags to prevent XSS:
$jsonObj['userList']='';
if (empty($jsonObj['errorMsg'])) {	
	$sql = "select userName,city,state from user_info where userIP='".$userIP."'";
	$rs = mysqli_query($db, $sql); $err = mysqli_error($db); if (!empty($err)) $jsonObj['errorMsg'] = $err;
	while($row = mysqli_fetch_assoc($rs)) {
		$jsonObj['userList'].= "<tr><td>".strip_tags($row['userName'])."</td><td>".strip_tags($row['city']).
				"</td><td>".strip_tags($row['state'])."</td></tr>";
	}
}

#Now send back the data in json format
echo json_encode($jsonObj);

Step 5:

Do something with the results! You could export them, feed them into another system using an API, send them in an email to someone, or just display them like so:

Name	City	State
You have not entered any user records yet, try it out!