Syntax:
\($\)file_Object = fopen("FileName", "Read/WriteMode") or die("Error Message!");

Syntax:
< input type="file" name="myFile" >

Syntax:
<Input type = "text" name = "name">

Validation is a process of checking the input data submitted by the user from client machine.

HTML form controls are used to collect data from user.

PHP write a File:
The fwrite( ) function is used to write to a file.
Syntax:
fwrite(＄myfile, ＄txt);
Example:
< ?php
＄myfile = fopen("new_schooLfile.
txt", "w'')
or die("Unable to open file!'');
＄txt = "School Name\n";
fwrite(＄myfile, ＄txt);
＄txt = "Student Name\n";
fwrite(＄myfile, ＄txt);
fclose(＄myfile);
? >

PHP Open a File
1. fopen( ) is a system function available in PHP.
2. This function helps to open a file in the server.
3. It contains two parameters one for the file and the other one specifies in which mode the file should be opened (Read/Write).
Syntax:
＄file_Object= . fopen("FileName", "Read/ WriteMode'') or die("Error Message!'');
Example:
< ?php
＄myfile = fopen("Student.txt", "r'') or die("Unable to open file!'');
? >

PHP provides a convenient way of working with files via collection of built in functions, some of the functions are file open, file read, file close, file write, Appending a file and uploading a file.
(i.e.): fopen(), fread(), fclose(), fwrite(), file_put_contents(), etc.

(i) To get form data, we need to use PHP $_GET and S_POST.
(ii) To retrieve data from get request, we need to use $_GET and for post request $_POST.
(iii) We can send limited amount of data through get request and large amount of data through post request.

File handling is an important activity of all web application development process.
Files are processed for different tasks using the following events :
(i) PHP Open a File,
(ii) PHP Read a File,
(iii) PHP Close a File,
(iv) PHP Write a File,
(v) PHP Appending a File and 
(vi) PHP uploading a File.
(1) PHP Open a File : fopen() is a system function available in PHP. This function helps to open a file in the server. It contains two parameters one for the file and the other one specifies in which mode the file should be opened (Read/Write).
Syntax:
$file_Object= fopen("FileName", "Read/
WriteMode") or die("Error Message!");
Example:

$myfile = fopen("Student.txt", "r")
or die("Unable to open file!");
?>
(ii) PHP Read a File: The fread() function reads from an open file. The file object comes from fopen function.
Syntax:
fread($file_Object,filesize("FileName"));
Example:

fread($myfile,filesize("Student.txt"));
?>
(iii) PHP Close a File: The fclose() function is used to close an opened file. The file object comes from fopen function.
Syntax:
fclose($file_Object);
Example:

(iv) PHP write a File: The fwrite() function is used to write to a file.
Syntax:

In the file handling process following task can be included
(i) open file for read and write
(ii) close file
(iii) perform operations on file
(iv) write results
With PHP we can handle file easily. There are various in built functions available for file handling for PHP.
Using file handling we can open, create, upload and edit files in PHP before working with file. We must open the file first using fopen() function.fopen() function is used in a following manner to perform this task.
＄fp = fopen(, )
In the above code, we have used two parameters while using fopen() function.
filename to open mode in which file is to be opened.
The function will return a file pointer if the file is successfully opened, otherwise it will return false.
Modes we use in the file handling

PHP Basic Form Handling:
(i) When the user keys in the input data in HTML controls and clicks the submit button the request will be generated and reaches a PHP file which is mentioned in the FORM tag under the Action attribute.
(ii) All the input values are synchronized and sent to the server via POST method or GET method. Method is an attribute of form tag in HTML.
(iii) Once the data reaches the server,two PHP variables such as \($\)_POST and \($\)_GET collects the data and prepares the response accordingly.
Post Method: The input data sent to the server with POST method is stored in the request body of the client's HTTP request.
Get Method: The input data sent to the server with POST method via URL address is known as query string. All input data are visible by user after they clicks the submit button.
Example:
Test.html:
< html >
< body >
<form action="'welcome.php" method=''post" >
Name: < input type="text" name="name'' > < br >
E-mail: < input type="text" name="email" > < br >
< input type=''submit" >
< /form >
< /body >
< /html >
Welcome.php:
< html >
< body >
Welcome < ?php echo  \($\)_POST["name"]; ? > < br >
Your email address is: < ?php echo  \($\)_POST["email"]; ? >
< /body >
< /html >
Output

(i) HTML File contains two Text Box (Name and Email), One Button and one form tag. The remote server PHP file (welcome.php) is mentioned in form tag under the Action Attribute.
(ii) In "Welcome.Php" file, PHP variables such as \($\)_POST and \($\)_GET collects the data and prepares the response accordingly.
(iii) Eventually the user will receive the output response in the client machine's browser screen.