Using if, else, or then statments to check vairables.

mlsbraves

I can't really figure out how to use these functions correctly and its a little different from what I learned in VB.net. I have a form that users fill out and when they submit it, the data is inserted into a mysql database. Problem is it will accept duplicates as well as nothing at all. So I need to check for that before it get submited.

I was thinking something like:

if($_POST["value"]=="") then die {echo "There was no value entered"}; Else
if( ($_POST["value"]=mysql_fetch_array(mysql_connect("localhost", "username", "pass", profiles (user); )  ) Then{echo "already excist"}; Else
Continue code

The synex is wrong and the code needs to check every row in the user field to see if the value matches and I know this is nowhere close but could I get some help here.

laserlight

set the required field as UNIQUE in the DB, or perhaps try to SELECT the incoming data from the DB first, and if there are rows returned, there will be a duplicate on a new INSERT.

mlsbraves

How would i set it up if that was the way I had to do it? I'm not sure how to use the if function.
if( ($_POST["value"]=mysql_fetch_array(mysql_connect("localhost", "username", "pass", profiles (user)) Then(echo "dup."); Else...

rehfeld

php doesnt have a "then" statement

you kinda just use curly braces


if ($foo == 'bar') {
    // then
    echo 'yes';
} else {
    echo 'no';
}

for the sql part, there are examples given in the manual

http://us2.php.net/manual/en/function.mysql-connect.php
http://us2.php.net/manual/en/function.mysql-select-db.php
http://us2.php.net/manual/en/function.mysql-query.php

laserlight

I think you need to learn PHP.
Check out Paul Hudson's Practical PHP Programming online book.
Since you have prior programming experience, you should be able to quickly absorb the material he presents.

Here's some sample code that I think should give you an idea of what to do, but only after you have actually learnt the basics of PHP:

//check that form element named "name" contains something
if (!empty($_POST['name'])) {
	//does a row with this value already exist in the DB?
	$query = "SELECT `name` FROM `tablename` WHERE `name`='{$_POST['name']}'";
	//note that we are sending a query with an unvalidated incoming variable
	//this is normally dangerous
	$result = mysql_query($query)
		OR die(mysql_error()); //practical development-stage error check
	//if no rows returned, then adding will result in no duplicates
	if (mysql_num_rows($result) == 0) {
		//insert the data as required
	} else {
		//row exists => value matches => error message
	}
}