Check If Email Address Is Already Exists in The Database

In this tutorial, you will learn how to check if email is already exists in the database using PHP & MySQL with Ajax. This task is needed if you are building applications in any programming language. You need to check if the email input is not yet existing in your database to prevent record duplication. But right now we will use PHP & MySQL for the sake of this tutorial.

 

 

So first I will create a function so that it will be re-usable if I need to check email to a different table. Here is the function I coded under my functions.php file.

function isEmailExists($db, $tableName, $email)
{
		// SQL Statement
		$sql = "SELECT * FROM ".$tableName." WHERE email='".$email."'";

		// Process the query
		$results = $db->query($sql);

		// Fetch Associative array
		$row = $results->fetch_assoc();

		// Check if there is a result and response to  1 if email is existing
		return (is_array($row) && count($row)>0);
}

 

Parameters:

$db - we need this for your SQL connection using mysqli object.

$tableName - we add the $tableName variable to put the table_name so that we can check any tables with possible checking of emails.

$email - your email string submitted from the form

 

Then next, we will call the function created above. Here is the code below for you to understand.

if(!isEmailValid($email)):
	$result['has_error'] = 1;
	$result['response'] = "Email address is invalid.";
elseif(isEmailExists($db, "employees", $email)):
	$result['has_error'] = 1;
	$result['response'] = "Email address is already exists.";
endif;

 

So we have if statement above first we check if the email is invalid and next are about if the email exists.

 

So here is the complete source code for the save.php for you to understand deeper.

<?php
	// include config file
	require_once 'config.php';

	//a PHP Super Global variable which used to collect data after submitting it from the form
	$request = $_REQUEST;
	//get email address value
	$email = $request['email']; 
	//get first name value
	$first_name = $request['first_name'];
	//get last name value 
	$last_name = $request['last_name'];
	//get address value
	$address = $request['address'];

	// Defined $result as array
	$result = [];
	
	if(!isEmailValid($email)):
		$result['has_error'] = 1;
		$result['response'] = "Email address is invalid.";
	elseif(isEmailExists($db, "employees", $email)):
		$result['has_error'] = 1;
		$result['response'] = "Email address is already exists.";
	endif;

	// Check if no errors
	if(!count($result)):
		// SQL Statement
		$sql = "INSERT INTO employees (email, first_name, last_name, address)
		VALUES ('".$email."', '".$first_name."', '".$last_name."', '".$address."')";

		// Process the query
		if ($db->query($sql)) {
		  $result['response'] = "Employee has been created.";
		} else {
		  $result['response'] = "Error: " . $sql . "<br>" . $db->error;
		}

		// Close the connection after using it
		$db->close();
	endif;

	// Encode array into json format
	echo json_encode($result);


?>

 

Then since we are using Ajax on this tutorial so here to code for the javascript inside scripts.js I call it save() function

function save() 
{
	$("#btnSubmit").on("click", function() {
		var $this 		    = $(this); //submit button selector using ID
        var $caption        = $this.html();// We store the html content of the submit button
        var form 			= "#form"; //defined the #form ID
        var formData        = $(form).serializeArray(); //serialize the form into array
        var route 			= $(form).attr('action'); //get the route using attribute action

        // Ajax config
    	$.ajax({
	        type: "POST", //we are using POST method to submit the data to the server side
	        url: route, // get the route value
	        data: formData, // our serialized array data for server side
	        beforeSend: function () {//We add this before send to disable the button once we submit it so that we prevent the multiple click
	            $this.attr('disabled', true).html("Processing...");
	        },
	        success: function (response) {//once the request successfully process to the server side it will return result here
	           
	        	response = JSON.parse(response);

	        	// Check if there is has_error property on json response from the server
	        	if(!response.hasOwnProperty('has_error')) {
		            // Reload lists of employees
		            all();

		            // We will display the result using alert
		            Swal.fire({
					  icon: 'success',
					  title: 'Success.',
					  text: response.response
					});

		            // Reset form
		            resetForm(form);
	        	} else {
	        		// We will display the result using alert
		            Swal.fire({
					  icon: 'warning',
					  title: 'Error.',
					  text: response.response
					});
	        	}

	        	$this.attr('disabled', false).html($caption);
	            
	        },
	        error: function (XMLHttpRequest, textStatus, errorThrown) {
	        	// You can put something here if there is an error from submitted request
	        }
	    });
	});
}

 

So that's all, I hope you learn from it and apply it to your project. You can also download the full source code of this tutorial for you to see in action.

 

 

Download

 

Thank you for reading. Happy Coding :)