Тег <form></form>

Этот тег определяет форму на веб-странице.

Аргумент	Значение
accept-charset	encoding
action	URL
autocomplete	on off
enctype	application/x-www-form-urlencoded multipart/form-data text/plain
method	get post
name	name_form
novalidate	novalidate
target	_blank _self _parent _top

index.php

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>Name Page</title>
</head>
<body>
<?php
if($_SERVER['REQUEST_METHOD'] == 'POST') {
$a = (string)trim(htmlspecialchars($_POST['a'], ENT_QUOTES));
if($_REQUEST['clear']) {
$a = null;
}
}
?>
<form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post">
<fieldset>
<legend>This data will send into a server</legend>
<br />
<input type="text" name="a" value="<?php echo $a; ?>" />
  
<label>Enter text</label>
<br />
<br />
<input type="submit" name="perform" value="Perform" />
  
<input type="submit" name="clear" value="   Clear   " />
<br />
<br />
</fieldset>
<br />
<fieldset>
<legend>Reading data from a server</legend>
<br />
<?php
if($_SERVER['REQUEST_METHOD']=='POST' && $_REQUEST['perform'] && !$_REQUEST['clear']) {
echo $a;
}
else {
echo null;
}
?>
<br />
<br />
</fieldset>
</form>
</body>
</html>

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>Name Page</title>
</head>
<body>
<?php
if($_SERVER['REQUEST_METHOD'] == 'POST') {
$a = (string)trim(htmlspecialchars($_POST['a'], ENT_QUOTES));
if($_REQUEST['clear']) {
$a = null;
}
}
?>
<form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post">
<fieldset>
<legend>This data will send into a server</legend>
<br />
<input type="text" name="a" value="<?php echo $a; ?>" />
  
<label>Enter text</label>
<br />
<br />
<input type="submit" name="perform" value="Perform" />
  
<input type="submit" name="clear" value="   Clear   " />
<br />
<br />
</fieldset>
<br />
<fieldset>
<legend>Reading data from a server</legend>
<br />
<?php
if($_SERVER['REQUEST_METHOD']=='POST' && $_REQUEST['perform'] && !$_REQUEST['clear']) {
echo $a;
}
else {
echo null;
}
?>
<br />
<br />
</fieldset>
</form>
</body>
</html>