trying to compare two email fields - page blanks out - php

Question

Right now, posting a snippet of what I wrote:
if (isset($_POST["email1"] != $_POST["email2"])) {
$email2Err = "please enter the same email address";
}
Every single time when I try to post the snippet above or a variation of it, it literally blanks out my page.
Question is, is the code I wrote above a good way to compare two email addresses via text fields?
And why does it blank out my entire page every time?
Here's a bit of further context if that's more helpful (let me know you want the entire page):
<?php
session_start(); //allows use of session variables
if ($_SERVER["REQUEST_METHOD"] == "POST") {
if (empty($_POST["nights"])) {
$nightsErr = "# of nights are required";
} else {
$nights = test_input($_POST["nights"]);
}
if (empty($_POST["arrivals"])) {
$arrivalsErr = "Time of arrival is required";
} else {
$arrivals = test_input($_POST["arrivals"]);
}
if (empty($_POST["male"])) {
$maleErr = "# of people (gender female) required";
} else {
$male = test_input($_POST["male"]);
}
if (empty($_POST["female"])) {
$femaleErr = "# of people (gender female) required";
} else {
$female = test_input($_POST["female"]);
}
if (empty($_POST["rooms"])) {
$roomsErr = "# of rooms required";
} else {
$rooms = test_input($_POST["rooms"]);
}
if (empty($_POST["type"])) {
$typeErr = "type of rooms required";
} else {
$type = test_input($_POST["type"]);
}
if (empty($_POST["name"])) {
$nameErr = "name required";
} else {
$name = test_input($_POST["name"]);
}
if (empty($_POST["address"])) {
$addressErr = "address required";
} else {
$address = test_input($_POST["address"]);
}
if (empty($_POST["zip"])) {
$zipErr = "zip required";
} else {
$zip = test_input($_POST["zip"]);
}
if (empty($_POST["telephone"])) {
$telephoneErr = "telephone required";
} else {
$telephone = test_input($_POST["telephone"]);
}
if (empty($_POST["email1"])) {
$email1Err = "email required";
} else {
$email1 = test_input($_POST["email1"]);
}
if (empty($_POST["email2"])) {
$email2Err = "email2 required";
} else {
$email2 = test_input($_POST["email2"]);
}
if (isset($_POST["email1"] != $_POST["email2"])) {
$email2Err = "please enter the same email address";
}
}
function test_input($data) {
$data = trim($data);
$data = stripslashes($data);
$data = htmlspecialchars($data);
return $data;
}
?>

Answer 1

This is failing you and isn't the right syntax for what you want to achieve:
if (isset($_POST["email1"] != $_POST["email2"]))
What you need to do is to first check if it is set then check if both are (not) equal to, but it's best to use !empty(), then check if it is not equal to:
if (!empty($_POST["email1"]) && !empty($_POST["email2"])) {
if ($_POST["email1"] != $_POST["email2"]) {
$email2Err = "Emails don't match. Please enter the same email address.";
}
}
Plus, make sure your form elements both have the right name attributes.
Also, a blank page can mean syntax errors.
Add error reporting to the top of your file(s) which will help find errors.
<?php
error_reporting(E_ALL);
ini_set('display_errors', 1);
// rest of your code
Sidenote: Displaying errors should only be done in staging, and never production.

Answer 2

What you are doing is assigning by using a single equals to sign rather make it a double equals to sign, I mean ==

Answer 3

Try:
if (isset($_POST["email1"]) && isset($_POST["email2"])) {
if ($_POST["email1"] != $_POST["email2"]) {
$email2Err = "please enter the same email address";
}
}