What reads php files

PHP File Open/Read/Close

In this chapter we will teach you how to open, read, and close a file on the server.

PHP Open File — fopen()

A better method to open files is with the fopen() function. This function gives you more options than the readfile() function.

We will use the text file, «webdictionary.txt», during the lessons:

AJAX = Asynchronous JavaScript and XML
CSS = Cascading Style Sheets
HTML = Hyper Text Markup Language
PHP = PHP Hypertext Preprocessor
SQL = Structured Query Language
SVG = Scalable Vector Graphics
XML = EXtensible Markup Language

The first parameter of fopen() contains the name of the file to be opened and the second parameter specifies in which mode the file should be opened. The following example also generates a message if the fopen() function is unable to open the specified file:

Example

$myfile = fopen(«webdictionary.txt», «r») or die(«Unable to open file!»);
echo fread($myfile,filesize(«webdictionary.txt»));
fclose($myfile);
?>

Tip: The fread() and the fclose() functions will be explained below.

The file may be opened in one of the following modes:

Modes	Description
r	Open a file for read only. File pointer starts at the beginning of the file
w	Open a file for write only. Erases the contents of the file or creates a new file if it doesn’t exist. File pointer starts at the beginning of the file
a	Open a file for write only. The existing data in file is preserved. File pointer starts at the end of the file. Creates a new file if the file doesn’t exist
x	Creates a new file for write only. Returns FALSE and an error if file already exists
r+	Open a file for read/write. File pointer starts at the beginning of the file
w+	Open a file for read/write. Erases the contents of the file or creates a new file if it doesn’t exist. File pointer starts at the beginning of the file
a+	Open a file for read/write. The existing data in file is preserved. File pointer starts at the end of the file. Creates a new file if the file doesn’t exist
x+	Creates a new file for read/write. Returns FALSE and an error if file already exists

PHP Read File — fread()

The fread() function reads from an open file.

The first parameter of fread() contains the name of the file to read from and the second parameter specifies the maximum number of bytes to read.

The following PHP code reads the «webdictionary.txt» file to the end:

PHP Close File — fclose()

The fclose() function is used to close an open file.

It’s a good programming practice to close all files after you have finished with them. You don’t want an open file running around on your server taking up resources!

The fclose() requires the name of the file (or a variable that holds the filename) we want to close:

PHP Read Single Line — fgets()

The fgets() function is used to read a single line from a file.

The example below outputs the first line of the «webdictionary.txt» file:

Example

$myfile = fopen(«webdictionary.txt», «r») or die(«Unable to open file!»);
echo fgets($myfile);
fclose($myfile);
?>

Note: After a call to the fgets() function, the file pointer has moved to the next line.

PHP Check End-Of-File — feof()

The feof() function checks if the «end-of-file» (EOF) has been reached.

The feof() function is useful for looping through data of unknown length.

The example below reads the «webdictionary.txt» file line by line, until end-of-file is reached:

Example

$myfile = fopen(«webdictionary.txt», «r») or die(«Unable to open file!»);
// Output one line until end-of-file
while(!feof($myfile)) echo fgets($myfile) . «
«;
>
fclose($myfile);
?>

PHP Read Single Character — fgetc()

The fgetc() function is used to read a single character from a file.

The example below reads the «webdictionary.txt» file character by character, until end-of-file is reached:

Example

$myfile = fopen(«webdictionary.txt», «r») or die(«Unable to open file!»);
// Output one character until end-of-file
while(!feof($myfile)) echo fgetc($myfile);
>
fclose($myfile);
?>

Note: After a call to the fgetc() function, the file pointer moves to the next character.

Complete PHP Filesystem Reference

For a complete reference of filesystem functions, go to our complete PHP Filesystem Reference.

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Files in PHP

Files play an important part in all sorts of programs, whether they are desktop-based or web-based. In this comprehensive lesson, we will go over all there is to know about files in PHP.

Reading Files in PHP

To access and read file contents, PHP provides the fopen() function. The fopen() function provides additional functionality than the readfile() method. We’ll be utilizing an example file called “my dictionary.txt” for this lesson. Its contents are as follows: certain technology-related abbreviations are followed by their full forms.

The fopen function accepts two parameters; the first parameter is the name of the file to open, and the second parameter is the mode in which the file should be open, such as read or write mode. If this function successfully opens the file, it returns its handle. In case of failure, you can print a message like in the following example:

$myfile = fopen("my_dictionary.txt", "r") or die("Unable to open file!"); echo fread($myfile,filesize("my_dictionary.txt")); fclose($myfile);

It’s important to remember that files might be a source of memory leakage, so be cautious while interacting with them.

Modes of Opening a File

You may open a file in a variety of ways. The modes are listed below, along with their descriptions:

• r: Open a file for read-only. The file pointer starts at the beginning of the file.
• w: Open a file for write-only. Erases the contents of the file or creates a new file if it doesn’t exist. The file pointer starts at the beginning of the file.
• a: Open a file for write-only. The existing data in the file is preserved. The file pointer starts at the end of the file. Creates a new file if the file doesn’t exist.
• x: Creates a new file for write-only. Returns false and an error if the file already exists.
• r+: Open a file for reading/write. The file pointer starts at the beginning of the file.
• w+: Open a file for reading/write. Erases the contents of the file or creates a new file if it doesn’t exist. The file pointer starts at the beginning of the file.
• a+: Open a file for reading/write. The existing data in the file is preserved. The file pointer starts at the end of the file. Creates a new file if the file doesn’t exist.
• x+: Creates a new file for reading/write. Returns false and an error if the file already exists.

Q&A

Q: Why is it important to close an open file in PHP?
A: It is critical to close an open file in PHP to avoid memory leaks, errors, and other problems. When a file is opened, it reserves a specific amount of memory, and if it is not correctly closed, it will continue to occupy that memory, potentially resulting in difficulties such as sluggish performance and system crashes. Furthermore, if a file is open, it may be impossible for other programs to remove or modify it.

Q: What is the difference between the “r”, “w”, and “a” modes when opening a file in PHP?
A: The “r” mode is used to open a read-only file, and the file pointer is set to the beginning of the file. The “w” mode is used to open a file for write-only purposes, wiping its contents or creating a new file if it does not already exist, and the file pointer is reset to the beginning of the file. The “a” mode is used to open a file for write-only access while retaining the file’s current contents; the file pointer starts at the end of the file and creates a new file if the file does not exist.

Q: Can you explain the concept of file pointers in PHP?
A: A file pointer is a cursor in PHP that refers to a particular position within a file. When you open a file, the file pointer is reset to the beginning of the file. The file pointer travels to different points inside the file when you read or write to it. This enables you to read or write to select areas inside a file rather than the full file at once.

Q: Can you name some of the functions in PHP to work with files?
A: fopen(), fread(), fwrite(), fclose(), and file_get_contents() are some of the most widely used file-related methods in PHP (). These functions can open and read files, write to files, close files, and retrieve file contents.

Q: What is the purpose of the filesize() function in PHP?
A: The PHP filesize() method is used to calculate the size of a file in bytes. To guarantee that the right amount of data is read from a file, this method is frequently used in conjunction with other file-related functions such as fread() or file_get_contents(). It may also be used to verify the size of a file before uploading it to a server or for other reasons of validation.

Exercises:

1. What function do you use in PHP to open a file for reading?
2. How can you check if a file exists in PHP before attempting to open it?
3. What function do you use in PHP to write data to a file?
4. How can you move a pointer to a specific location within a file in PHP?
5. How can you delete a file in PHP?

Answers:

1. fopen() function is used to open a file for reading in PHP.
2. You can use the file_exists() function to check if a file exists before attempting to open it in PHP.
3. fwrite() function is used to write data to a file in PHP.
4. fseek() function is used to move a pointer to a specific location within a file in PHP.
5. unlink() function is used to delete a file in PHP.

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