1. Determine if a file/directory exists

is_file function

• is_file — Determines whether the given file name is a regular file. Returns TRUE if the file exists and is a regular file, FALSE otherwise.
• Official documentation: http://php.net/manual/en/function.is-file.php

is_dir function

• is_dir() function checks if a specified file is a directory. Returns TRUE if the file name exists and is a directory, FALSE otherwise.
• Official documentation: http://php.net/manual/en/function.is-dir.php

file_exists() function

• file_exists() function checks whether a file or directory exists. Returns true if the specified file or directory exists, false otherwise. It is like a combination of the previous two functions.
• More information: PHP file_exists() function

2. Read a file

file_get_contents() function

• file_get_contents — Reads entire file into a string.
• Official documentation: http://php.net/manual/en/function.file-get-contents.php

fread() function

Example of reading a file:

<?php
 $file = fopen("test.txt","r");
 fread($file,filesize("test.txt"));
 fclose($file);
?>

More information: PHP fread() function

3. Write to a file

PHP fread() function

Example:

<?php
 $myfile = fopen("newfile.txt", "w") or die("Unable to open file!");
 $txt = "Bill Gates\n";
 fwrite($myfile, $txt);
 fclose($myfile);
?>

More information: PHP File Creation/Writing

file_put_contents() function

• file_put_contents — Writes a string to a file, similar to using fopen(), fwrite(), and fclose() together.
• Usage: file_put_contents('filename','filedata')
• Official documentation: http://php.net/manual/en/function.file-put-contents.php

4. Create directory/delete/copy

mkdir function, create directory

• Usage: mkdir('filename','mode'), default mode is 0777 with maximum permissions.
• Returns: TRUE on success, or FALSE on failure.
• Official documentation: http://php.net/manual/en/function.mkdir.php

rmdir function, delete directory

• Returns: TRUE on success, or FALSE on failure.
• Official documentation: http://php.net/manual/en/function.rmdir.php

unlink function, delete file

• Returns: TRUE on success, or FALSE on failure.
• Official documentation: http://php.net/manual/en/function.unlink.php

copy() function, copy file

• Syntax: copy(source,destination)
• Returns: Copies the file from source to destination. Returns TRUE on success, or FALSE on failure.
• More information: PHP copy() function

rename() function

• rename() function renames a file or directory.
• Syntax: rename(oldname,newname,context)
• Returns: Returns true if successful, false otherwise.

move_uploaded_file() function

• move_uploaded_file() function moves an uploaded file to a new location.
• Syntax: move_uploaded_file(file,newloc)
• Returns: Returns true on success, false on failure.