PHP and Files

Working with files in PHP is painless, with methods that should feel familiar when compared to other languages you have worked with. For example:

<?php
  $fileName = '';
  if (isset($_GET['filename'])) {
    $fileName = $_GET['filename']; //get the file names from params
    $fp = fopen($fileName, 'r');   //open the file for reading 
    if (!$fp) {                    //check that file opened ok
      echo "<p>ERROR! Could not open file $fileName for reading.</p>";
    } else {
      $line = fgets($fp);          // read a line
      while( !feof($fp) ) {        //while end of file not reached
        $content = $content . $line . '<br>';
        $line = fgets($fp);
      }
    }
    fclose($fp);                   //close the file
  }
?>

Writing to file

int fwrite(filePointer, string [, length])

Reading from a file

//read one line from file, including the newline character, up to maxLength-1 bytes if that param is provided

string fgets(filePointer, [maxLength])  

//secure read line: read one line from the file, including the newline character, and strip all the HTML tags; if maxLength provided, read up to maxLength-1 bytes from file; if allowableTags provided, do not strip those tags from the string returned

string fgetss(filePointer, [maxLength] [, allowableTags])

//read one line, split it by delimiter (comma by default) into an array and return the array

array fgetcsv(filePointer, [maxLength] [, string delimeter])

Reading the whole file

int readfile(fileName) //open file, echo content, close file
int fpassthru(filePointer) //read file starting with current position, echo content, close file
array file(fileName) //open file, read file content into array, each element being a line (including newline character), close file
string file_get_contents(fileName) //open file, read entire content into string, close file
  

Reading portions of a file

char fgetc(filePointer)  //read one character
string fread(filePointer, nbBytes)  //read up to nbBytes
  

Useful file functions

bool file_exists(filename)  //returns TRUE if file exists, FALSE otherwise
int filesize(filename) //returns the size of file in bytes, or FALSE if error
bool unlink(filename)  //deletes a file
  

Locking a file

$fp = fopen($fileName, 'a');
flock($fp, LOCK_EX); //acquire exclusive lock before write (LOCK_SH before read)
fwrite($fp, $text);
flock($fp, LOCK_UN);  //release lock
fclose($fp);

Debugging

Practice Problems

1. Create a text file called php-practice.txt with the following content:
   
   

   Navy Spirit Gear Hat,10,5.50
   Navy Birthday T-shirt XL,13,12.95
   Navy Blue Baseball Cap,42,9.95
   Ball Point Pen,31,1.05
   Navy Pride Bumper Sticker,16,4.99

   Write a .php script that will read the contents of this file, and place the results into an associative array in the following format:
   
   

   array('Navy Spirit Gear Hat'=>array('quantity'=>10, 'price'=>5.50))

   which will allow you to access the contents via the array in the following way:
   
   

   $itemPrice = $myArray['Navy Spirit Gear Hat']['price'];

   This script should read in the name, quantity, price information from the php-practice.txt file and print the final array via the print_r() function. Take a look at PHP's explode function to determine how to split the string based on the comma in the text file.
2. Continuing... Use the associative array from part 1, to create an HTML table, with HTML output similar to (feel free to make better table code!):
   
   

   <table>
     <thead>
       <tr><th>Item</th><th>Quantity</th><th>Price</th></tr>
     </thead>
     <tbody>
       <tr><td>Navy Spirit Gear Hat</td><td>10</td><td>5.50</td></tr>
     </tbody>
   </table>

3. Continuing... Add to the table an input box to allow a customer to select a quantity for each item (similar to in-class example from the previous lecture). Set up the appropriate <form> and allow the user to submit their selections. Set the form method="POST" action="php-practice.php" (or based on the name of your php script) so the same script handles the requests. What do you plan to name your text box's? You will need to be able to access the information when it is submitted.
4. Continuing... Check to see if the user submitted an order, if so print out the order (including item, quantity, cost per item, and total cost), otherwise print out the form. Remember the data from the form will be provided in the $_POST variable (which is an associative array)