To obtain form data through $_POST in PHP, you must ensure that the field name matches, check the submission method and pay attention to safe processing. Use the $_POST hyperglobal variable to directly obtain the corresponding value based on the name attribute of the form field; 1. Ensure that the key name in the PHP code is consistent with the name attribute of the HTML form; 2. Use $_SERVER['REQUEST_METHOD'] or isset functions to determine whether the data has been submitted; 3. Use functions such as htmlspecialchars or filter_input to filter and verify user input to prevent security risks; 4. For array data such as check boxes, the HTML field name should be written in hobbies[] format so that PHP can correctly receive it as an array.

When processing form submission in PHP, if your form uses the POST method, you can use the hyperglobal variable $_POST to obtain the user submitted data.

Basic usage

Suppose you have the following HTML form:

 <form method="post" action="process.php">
  <input type="text" name="username">
  <input type="password" name="password">
  <button type="submit">Submit</button>
</form>

When the user clicks the "Submit" button, the data will be sent to the process.php file. In this file, you can access this data like this:

 <?php
$username = $_POST[&#39;username&#39;];
$password = $_POST[&#39;password&#39;];

echo "Username is:" . $username;
// Note: Don&#39;t output password directly, this is just for demonstration?>

As long as name attribute is set in the form field, the corresponding value can be obtained through $_POST['name值'] .

Frequently Asked Questions and Notes

1. Make sure the field names match

$_POST is used to obtain data based on name attribute of the form field, not id or other attribute. So be sure to make sure that the key names you use in PHP are consistent with name value in the HTML form.

For example, the following example cannot obtain the value:

 <input type="text" id="username" name="user_name">

The corresponding PHP should be:

 $username = $_POST['user_name']; // Correct // instead of $_POST['username']

2. Check whether there are actually submitted data

It is best to judge whether any data has been submitted before writing logic, otherwise an error may be reported.

You can do this:

 if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    // Process POST data}

Or to more specifically determine whether a field exists:

 if (isset($_POST['username'])) {
    // Username field has been submitted}

3. Prevent security risks

Although $_POST is convenient, it is risky to use the content entered by the user directly. Especially when you are going to insert this data into the database or display it on a page, be sure to do appropriate filtering and escape.

For example:

 $username = htmlspecialchars($_POST['username']);

You can also verify it in combination with filter_input() function:

 $email = filter_input(INPUT_POST, 'email', FILTER_VALIDATE_EMAIL);
if ($email) {
    // It's a legal mailbox}

4. Process form fields in array form

Sometimes you would like to submit multiple values ??at once, such as checkboxes:

 <input type="checkbox" name="hobbies[]" value="reading"> Reading <input type="checkbox" name="hobbies[]" value="coding"> Programming

At this time, what PHP receives is an array:

 $hobbies = $_POST['hobbies'];
foreach ($hobbies as $hobby) {
    echo $hobby . &#39;<br>&#39;;
}

Note: The field names in HTML must be written as hobbies[] to be correctly recognized as an array.

Basically that's it. PHP's $_POST is simple and direct to use, but you should also pay attention to the field name, security, and submission method. By mastering these details, you can basically cope with most form processing scenarios.

The above is the detailed content of How do I access form data submitted via POST using the $_POST superglobal?. For more information, please follow other related articles on the PHP Chinese website!