How to delete duplicate lines in text files in php, _PHP tutorial

How to delete duplicate lines in text files in php,

The example in this article describes how to delete duplicate lines in text files in php. Share it with everyone for your reference. The specific analysis is as follows:

This php function is used to delete duplicate lines in the file. You can also specify whether to ignore case and specify the newline character

/**
 * RemoveDuplicatedLines
 * This function removes all duplicated lines of the given text file.
 *
 * @param   string
 * @param   bool
 * @return  string
 */
function RemoveDuplicatedLines($Filepath, $IgnoreCase=false, $NewLine="\n"){
  if (!file_exists($Filepath)){
    $ErrorMsg = 'RemoveDuplicatedLines error: ';
    $ErrorMsg .= 'The given file ' . $Filepath . ' does not exist!';
    die($ErrorMsg);
  }
  $Content = file_get_contents($Filepath);
  $Content = RemoveDuplicatedLinesByString($Content, $IgnoreCase, $NewLine);
  // Is the file writeable?
  if (!is_writeable($Filepath)){
    $ErrorMsg = 'RemoveDuplicatedLines error: ';
    $ErrorMsg .= 'The given file ' . $Filepath . ' is not writeable!';  
    die($ErrorMsg);
  }
  // Write the new file
  $FileResource = fopen($Filepath, 'w+');   
  fwrite($FileResource, $Content);    
  fclose($FileResource);  
}
 
/**
 * RemoveDuplicatedLinesByString
 * This function removes all duplicated lines of the given string.
 *
 * @param   string
 * @param   bool
 * @return  string
 */
function RemoveDuplicatedLinesByString($Lines, $IgnoreCase=false, $NewLine="\n"){
  if (is_array($Lines))
    $Lines = implode($NewLine, $Lines);
  $Lines = explode($NewLine, $Lines);
  $LineArray = array();
  $Duplicates = 0;
  // Go trough all lines of the given file
  for ($Line=0; $Line < count($Lines); $Line++){
    // Trim whitespace for the current line
    $CurrentLine = trim($Lines[$Line]);
    // Skip empty lines
    if ($CurrentLine == '')
      continue;
    // Use the line contents as array key
    $LineKey = $CurrentLine;
    if ($IgnoreCase)
      $LineKey = strtolower($LineKey);
    // Check if the array key already exists,
    // if not add it otherwise increase the counter
    if (!isset($LineArray[$LineKey]))
      $LineArray[$LineKey] = $CurrentLine;    
    else        
      $Duplicates++;
  }
  // Sort the array
  asort($LineArray);
  // Return how many lines got removed
  return implode($NewLine, array_values($LineArray));  
}

Usage example:

// Example 1
// Removes all duplicated lines of the file definied in the first parameter.
$RemovedLinesCount = RemoveDuplicatedLines('test.txt');
print "Removed $RemovedLinesCount duplicate lines from the test.txt file.";
// Example 2 (Ignore case)
// Same as above, just ignores the line case.
RemoveDuplicatedLines('test.txt', true);
// Example 3 (Custom new line character)
// By using the 3rd parameter you can define which character
// should be used as new line indicator. In this case
// the example file looks like 'foo;bar;foo;foo' and will
// be replaced with 'foo;bar' 
RemoveDuplicatedLines('test.txt', false, ';');

I hope this article will be helpful to everyone’s PHP programming design.

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