File Handling in PHP

Replies

• 

  PraveenKumar Purushothaman

  File Modes
  
  File Modes
  The following list shows the different modes the file may be opened in.
  

  Mode r
  Read Only mode, with the file pointer at the start of the file.
  
  Mode r+
  Read/Write mode, with the file pointer at the start of the file.
  
  Mode w
  Write Only mode. Truncates the file (effectively overwriting it). If the file doesn't exist, fopen will attempt to create the file.
  
  Mode w+
  Read/Write mode. Truncates the file (effectively overwriting it). If the file doesn't exist, fopen will attempt to create the file.
  
  Mode a
  Append mode, with the file pointer at the end of the file. If the file doesn't exist, fopen will attempt to create the file.
  
  Mode a+
  Read/Append, with the file pointer at the end of the file. If the file doesn't exist, fopen will attempt to create the file.

  Note: The mode may also contain the letter 'b'. This is useful only on systems which differentiate between binary and text files (i.e.Windows. It's useless on Unix/Linux). If not needed, it will be ignored.
• 

  PraveenKumar Purushothaman

  Closing a File
  
  Closing a File
  The fclose function is used to close a file when you are finished with it.
  

  fclose($fp);
• 

  PraveenKumar Purushothaman

  Reading from Files
  
  Reading from Files
  You can read from files opened in r, r+, w+, and a+ mode. The feof function is used to determine if the end of file is true.
  

  if ( feof($fp) )
    echo "End of file
";

  The feof function can be used in a while loop, to read from the file until the end of file is encountered. A line at a time can be read with the fgets function:
  

  while( !feof($fp) ) {
    // Reads one line at a time, up to 254 characters. Each line ends with a newline.
    // If the length argument is omitted, PHP defaults to a length of 1024.
    $myline = fgets($fp, 255);
    echo $myline;
}

  You can read in a single character at a time from a file using the fgetc function:
  

  while( !feof($fp) ) {
    // Reads one character at a time from the file.
    $ch = fgetc($fp);
    echo $ch;
}

  You can also read a single word at a time from a file using the fscanf function. The function
  takes a variable number of parameters, but the first two parameters are mandatory. The first
  parameter is the file handle, the second parameter is a C-style format string. Any parameters
  passed after this are optional, but if used will contain the values of the format string.
  

  $listFile = "list.txt"; // See next page for file contents
if (!($fp = fopen($listFile, "r")))
    exit("Unable to open $listFile.");
while (!feof($fp)) {
    // Assign variables to optional arguments
    $buffer = fscanf($fp, "%s %s %d", $name, $title, $age);
    if ($buffer == 3) // $buffer contains the number of items it was able to assign
        print "$name $title $age
\n";
}

  Here is the file list.txt:
  

  Dave Programmer 34
  Sue Designer 21
  Lisa Programmer 29
  Nigel User 19

  You can also store the variables in an array by omitting the optional parameters in fscanf:
  

  while (!feof($fp)) {
    $buffer = fscanf($fp, "%s %s %d"); // Assign variables to an array
    // Use the list function to move the variables from the array into variables
    list($name, $title, $age) = $buffer;
    print "$name $title $age
\n";
}

  You can read in an entire file with the fread function. It reads a number of bytes from a file, up to the end of the file (whichever comes first). The filesize function returns the size of the file in bytes, and can be used with the fread function, as in the following example.
  

  $listFile = "myfile.txt";
if (!($fp = fopen($listFile, "r")))
    exit("Unable to open the input file, $listFile.");
$buffer = fread($fp, filesize($listFile));
echo "$buffer
\n";
fclose($fp);

  You can also use the file function to read the entire contents of a file into an array instead of opening the file with fopen:
  

  $array = file(‘filename.txt’);

  Each array element contains one line from the file, where each line is terminated by a newline.
• 

  PraveenKumar Purushothaman

  Writing to Files
  
  Writing to Files
  The fwrite function is used to write a string, or part of a string to a file. The function takes three parameters, the file handle, the string to write, and the number of bytes to write. If the number of bytes is omitted, the whole string is written to the file. If you want the lines to appear on separate lines in the file, use the \n character.
  Note: Windows requires a carriage return character as well as a new line character, so if you're using Windows, terminate the string with \r\n. The following example logs the visitor to a file, then displays all the entries in the file.
  

  < ?php
$logFile = "stats.txt";
$fp = fopen($logFile, "a+"); // Open the file in append/read mode
$userDetails = $_SERVER[‘HTTP_USER_AGENT’]; // Create a string containing user details
if (isset($_SERVER[‘HTTP_REFERER’]))
    $userDetails .= " {$_SERVER[‘HTTP_REFERER’]}
\r\n";
else
    $userDetails .= "
\r\n";
fwrite($fp, "$userDetails"); // Write the user details to the file
rewind($fp); // Move the file pointer to the start of the file
$entries = 0;
while(!feof($fp)) { // Display each line in the file
    $buffer = fgets($fp, 1024);
    if ($buffer != "") {
        echo $buffer;
        $entries++;
    }
} // Show a summary
echo "There are $entries entries in the log file
";
fclose ($fp);
? >

  I have added an extra space between

  php and ? >

  so that the board doesn't hang!