PHP How to check if text field matches var - php

Question

Well then, this is likely to be the n-th time someone is asking this, but honestly I didn't grab anything useful spending the last hour or so on Google. What I want to do is rather trivia, or so I thought. I have this working in Java Script but want to move it to PHP. In brief:
declare a var with a static value
add text field into which user is asked to enter value of above var
check if field is a) empty, b) non-empty mismatch, or c) non-empty match
My (limited) PHP wisdom has lead me into believing it ought to be something like the below, but apparently it's not. I'd very much appreciate any insight, tha.
<?php
$coconew = "blah";
if (isset ($_POST["cocosub"])) {
if ($_POST["cocoval"] == "") {
echo "empty";
} else {
if ($_POST["cocoval"] != $coconew) {
echo "mismatch";
} else {
echo "match";
}
}
}
?>
<form action="<?php $_SERVER['PHP_SELF'] ?>" id="cocosub" method="post">
<div>
<?php echo $coconew; ?>
<input type="text" id="cocoval">
<input type="submit">
</div>
</form>

Answer 1

You need to change
<input type="text" id="cocoval">
to
<input type="text" name="cocoval">
There are other (and probably better) ways to do this, but you are on the right track.

Answer 2

$_POST only looks for the name attribute of form elements, so modify your form as such:
<?php
$coconew = "blah";
if (isset ($_POST["cocoval"])) {
if ($_POST["cocoval"] === "") {
echo "empty";
} else {
if ($_POST["cocoval"] !== $coconew) {
echo "mismatch";
} else {
echo "match";
}
}
}
?>
<form id="cocosub" method="post">
<div>
<?php echo $coconew; ?>
<input type="text" id="cocoval" name="cocoval">
<input type="submit">
</div>
</form>
(I made a few other changes, you want to check isset on the element, not the form, it will POST to the same page if you don't give it an attribute [so no need to add the echo], and adding better type checking in your php)

Answer 3

in addition to the other answers already posted, you might also be interested in PHP's session support (depending on how "static" you need your static variables to be). That's where you'd put $cocoval and any other variables if you need to save their values across multiple requests for the same URL by the same user. See here for more info:
http://php.net/manual/en/features.sessions.php and
http://www.php.net/manual/en/book.session.php

Answer 4

This works:
<?php
session_start();
if(isset($_POST["cocosub"])){
$input = trim($_POST["cocoval"]);
if($input == ""){
echo "empty";
} elseif($input != $_SESSION["coconew"]){
echo "mismatch";
} else {
echo "match";
}
}
$_SESSION["coconew"] = substr(md5(uniqid()), 0, 5);
?>
<form action="<?php echo $_SERVER['PHP_SELF']; ?>" id="cocosub" method="post">
<div>
<?php echo $_SESSION["coconew"]; ?>
<input type="text" id="cocoval" name="cocoval">
<input type="submit" name="cocosub">
</div>
</form>
You needed to add name="cocosub" to the Submit button element in order for the first if(isset(...)) condition to be true. That's why the script didn't work. Also, instead of id, you need to use the name="cocoval" in the input text field as well in order for it to carry over into $_POST.