PHP File Handling

scandir(‘path’)	Will scan the files in the requesting directory. Will only do the first level.
is_dir(“path”)	Will return a boolean on whether or not a path is a directory.
fopen(‘file’, ‘mode’)	A function that opens a connection to a file and returns a file handler.
fclose($file_handler)	Will chose the file handler and close the file.
feof($file_handler)	Returns of a boolean of whether or not you are at the end of the file.
fgets($file_handler)	Will get the line and move the pointer to the next line.
strpos($line, $regex)	Will check if a string contains the regex line (Like .contains() in java).
str_replace(‘pattern’, ‘replaced_pattern’, $string)	Will replace a pattern in a string with a different pattern.
file_put_contents(‘path_to_file’)	Will get the entire contents of the file and store it as a string.
file(‘path_to_file’)	Will store the contents of a file as a string.
fwrite($file_handler, ‘string’)	This function will write a string to a file.
strcasecmp($a, $b)	A capitalized and binary safe way to compare strings.
strip_tags($str)	Will strip any HTML tags off a string.
usort($array, ‘function_name’)	Will sort an array based on the function fed into it.
file_put_contents()	Will write an array to a file using the write mode or the append mode.
fgetcsv($fh)	Will return a line of csv as an array
array_flip($array)	Will flip an array such that the key is the value and the value is the key.
extract($array)	Will pull out the keys of an array into its own variable.
fputcsv($fh, $array)	Puts a new line in csv format to the end of a file.
json_decode($str)	Turns a string of JSON into a PHP object.
is_object()	Will check if a variable is an object.
json_encode($books, JSON_PRETTY_PRINT	JSON_UNESCAPED_SLASHES);
opendir($dir)	Will open the entire directory as a file holder.
readdir($fh)	Will read the name of each file in the open directory.
$xml->addChild(‘item’, opt ‘value’)	Add items to an XML file.
$xml->asXML($file)	Load the XML data into the file.

Directory and File Structures:

• Everything on a computer is stored on some sort of file.
• Opening and processing a file is common for application:
  • Opening and interpreting a config file.
  • Exporting data/order details.
• Permissions control who has access to files. If a file cannot be opened, be sure to view its permissions.
• Recall:
  • . is the current directory
  • .. is the parent directory
  • Any file that starts with a dot is a hidden file.
• is_dir(‘path’) will return a boolean on whether or not a path is a directory.

Including and Opening files:

• When working with HTML files, you can use the include tag to add HTML.
  • Ex: <?php include 'data/html/countries.html'; ?>
• fopen(‘path’, ‘mode’) is a function that opens a connection to a file and returns a file handler.
  • It is good to include this function in an if statement in case the file load fails.
• fclose($file_handler) is a function that will close the file handler and the file.
• feof($fh) will return a boolean of whether or not you are at the end of a file.
• fgets($fh) will grad the line and move the pointer to the next line.
• str_replace() is a function that will replace a section of a string with another piece.

Reading Files Into a String or Array

• file_put_contents(“path”) will get the contents of the entire file and store it as a string.
• file(‘path’) will store the contents of the file as an array.
• Three Ways to Interact with a File:
  • Open a connection to the file and handle it line-by-line before closing it
  • Work with the entire file as a string
  • Work with the entire file as an object or array.

Writing Files Line by Line:

• Writing files allows you to change files to update what is going one.
• You can open the file for writing by using the ‘w’ mode:
  • fopen(‘file_name’, ‘w’);
  • This will erase the contents, so be careful!
• fwrite($file_handler, ‘string’)
• PHP_EOL.’string’ will add the proper end of line character when writing a file.

Writing Files All at Once:

• Adding FILE_IGNORE_NEW_LINES to the file() function will make it ignore all the newline characters \n.
• strcasecmp() is a binary safe string comparison function.
• strip_tags() will strip the HTML tags off of a string.
• usort($array, ‘function_name’) is a function that will sort an array based on the function fed into it.
• file_put_contents(‘file_path’, ‘string’) will write the contents of a string to a file.

Personal Recommendations Project:

• Most popular file types:
  • CSV
  • JSON
  • XML

Reading CSV:

• CSV stands for comma separated values
• Normally contains a header, and then the values below it.
• fgetcsv() will return an array of columns but only the line it is on.
  • The first line will be the headers!
• Be sure to store the headers so you can use them when working with the rest of the file.

Writing CSV:

• Start by making an array of the values you want to add.
• Use the fputcsv($fh, $array) function to add a csv line to a file.
• Be sure to ensure that there is a newline before adding to a CSV.
• fseek($fh, offset, whence) can change where the pointer is located when viewing a file.

Reading JSON:

• JSON is an easy way to encode structured data. It is fairly easy for humans to read it.
• JSON - Javascript Object Notation.
• JSON can be converted into Objects or arrays.
• json_decode() turns a string into a PHP object.
• is_object() will check if a variable is an object.
• You can access the object by using ->.

Writing JSON:

• json_encode can be used to turn a PHP object back into JSON.

Reading XML:

• XML is a lot more detailed than JSON.
• Used for rss feeds for blogs or podcasts.
• When displaying XML, you need to include htmlspecialchars() so that the tags show up.
• To open a whole directory, you can use the opendir() command.
• readdir($fh) will read the file name of an open directory.
• simplexml_load_file($file) will load the XML file into a PHP object.
• This object can be accessed using the object syntax for PHP.

Writing XML:

• To add data to an xml file, you use the addChild() function
  • The function takes two arguments
    • Key
    • Value
• XML does allow namespacing