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Form Validation Confusion

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Form Validation Confusion

Postby TheFoolontheHill » Thu Jan 09, 2014 9:49 am

Hi, newbie here. I have taken the PHP course at Codecademy and currently am doing PHP at w3scools.
The code provided below works, but I don't understand how the decision is made to echo a particular message in the <form> section (error or otherwise). I see that in the if statements that a message is assigned to variables, but where is the decision made to echo a particular variables value? I would appreciate it if someone could explain it to me.
Thank You,
TheFoolontheHill

Code: Select all
<!DOCTYPE html>
<html>
   <head>
      <link type="text/css" rel="stylesheet" href="style.css"/>
      <meta charset="utf-8">
      <title>PHP Form Validation Example</title>
        <style>.error {color: #FF0000;}</style>
   </head>
   <body>
   
   
<?php
// define variables and set to empty values
$nameErr = $emailErr = $genderErr = $websiteErr = "";
$name = $email = $gender = $comment = $website = "";

if ($_SERVER["REQUEST_METHOD"] == "POST")
{
    if (empty($_POST["name"]))
    {
        $nameErr = "Name is required";
    }
    else
    {
        $name = test_input($_POST["name"]);
        // check if name only contains letters and whitespace
        if (!preg_match("/^[a-zA-Z ]*$/",$name))
        {
            $nameErr = "Only letters and white space allowed";
        }
    }
   
    if (empty($_POST["email"]))
    {
        $emailErr = "Email is required";
    }
    else
    {
        $email = test_input($_POST["email"]);
        // check if e-mail address syntax is valid
        if (!preg_match("/([\w\-]+\@[\w\-]+\.[\w\-]+)/",$email))
        {
            $emailErr = "Invalid email format";
        }
    }
   
    if (empty($_POST["website"]))
    {
        $website = "";
    }
    else
    {
        $website = test_input($_POST["website"]);
        // check if URL address syntax is valid (this regular expression also allows dashes in the URL)
        if (!preg_match("/\b(?:(?:https?|ftp):\/\/|www\.)[-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i",$website))
        {
            $websiteErr = "Invalid URL";
        }
    }
   
    if (empty($_POST["comment"]))
    {
        $comment = "";
    }
    else
    {
        $comment = test_input($_POST["comment"]);
    }
   
    if (empty($_POST["gender"]))
    {
        $genderErr = "Gender is required";
    }
    else
    {
        $gender = test_input($_POST["gender"]);
    }
}

function test_input($data)
{
     $data = trim($data);
     $data = stripslashes($data);
     $data = htmlspecialchars($data);
     return $data;
}
?>

<h2>PHP Form Validation Example</h2>
<p><span class="error">* required field.</span></p>
<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>">
   Name: <input type="text" name="name" value="<?php echo $name;?>">
   <span class="error">* <?php echo $nameErr;?></span>
   <br><br>
   E-mail: <input type="text" name="email" value="<?php echo $email;?>">
   <span class="error">* <?php echo $emailErr;?></span>
   <br><br>
   Website: <input type="text" name="website" value="<?php echo $website;?>">
   <span class="error"><?php echo $websiteErr;?></span>
   <br><br>
   Comment: <textarea name="comment" rows="5" cols="40"><?php echo $comment;?></textarea>
   <br><br>
   Gender:
   <input type="radio" name="gender" <?php if (isset($gender) && $gender=="female") echo "checked";?>  value="female">Female
   <input type="radio" name="gender" <?php if (isset($gender) && $gender=="male") echo "checked";?>  value="male">Male
   <span class="error">* <?php echo $genderErr;?></span>
   <br><br>
   <input type="submit" name="submit" value="Submit">
</form>

<?php
echo "<h2>Your Input:</h2>";
echo $name;
echo "<br>";
echo $email;
echo "<br>";
echo $website;
echo "<br>";
echo $comment;
echo "<br>";
echo $gender;
?>
      
   </body>
</html>
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