how to show error message if someone left a field blank
So I created this page where a user can send data to a msql database but when they leave a field blank and they click submit I want an error to show up saying "You left a field blank".
This is the code:
<?php
$hostname = "";
$db_user = "";
$db_password = "";
$database = "";
$db_table = "";
# STOP HERE
####################################################################
# THIS CODE IS USED TO CONNECT TO THE MYSQL DATABASE
$db = mysql_connect($hostname, $db_user, $db_password);
mysql_select_db($database,$db);
?>
<html>
<head>
<title>Add your url to out database</title>
</head>
<body>
<?php
if (isset($_REQUEST['Submit'])) {
# THIS CODE TELL MYSQL TO INSERT THE DATA FROM THE FORM INTO YOUR MYSQL TABLE
$sql = "INSERT INTO $db_table(title,description,url,keywords) values ('".mysql_real_escape_string(stripslashes($_REQUEST['title']))."','".mysql_real_escape_string(stripslashes($_REQUEST['description']))."','".mysql_real_escape_string(stripslashes($_REQUEST['url']))."','".mysql_real_escape_string(stripslashes($_REQUEST['keywords']))."')";
if($result = mysql_query($sql ,$db)) {
echo '<h1>Thank you</h1>Your information has been entered into our database<br><br>';
} else {
echo "ERROR: ".mysql_error();
}
} else {
?>
<h1><center><img src='addalink.png'><center></h1>
<hr>
<center>
<form method="post" action="">
Name of the song:<br>
<input type="text" name="title"><br>
Artist: <br>
<input type="text" name="description"><br>
Download link: <br>
<font color="#0000FF">http://</font><input type="text" name="url"><br>
<input type="submit" name="Submit" value="Submit">
</form></b开发者_JAVA百科r>
<?php
}
?> <center>
</body>
</html>
First of all, use a CSS style to style your form's inputs. It's a lot easier to read, and it means if you need to change anything in the future it's quick.
What you're wanting to do is run a script on submit that checks whether or not the values in the required fields are what you expect.
The jQuery Validation Plugin - http://bassistance.de/jquery-plugins/jquery-plugin-validation/ takes care of what you want.
If you want to write your own, it's a process of attaching the validation function to the click event of the submit button (or the onSubmit event of the form) and checking the data that's in the form. If the data is missing, you add a class to show this. If the data is valid, you remove the previous class.
Finally, you only return true (to submit the form) in the case everything validates.
Keep in mind this is only client side, you still need to validate your data server side for security.
So, the common response is "do this on the front-end". If anything you are posting has security implications then I'd also recommend you check your form data on the back-end.
Also if you're going to go through the process of using mysql_real_escape, you might as well use mysqli and parameterized queries see: http://us2.php.net/manual/en/mysqli-stmt.prepare.php.
If you choose to go the back-end route, especially if you are using AJAX for the post, you can throw an Exception that actually outputs a 500 error along with the message you want to display, and then use Javascript to handle the "error case", so you can provide really nice validation methods that still do the validation on the server side.
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