Remove duplicated lines

This function removes all duplicated lines of a text file. That's it.

 * 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!';
    $Content = file_get_contents($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!';    
    // Write the new file
    $FileResource = fopen($Filepath, 'w+');      
    fwrite($FileResource, $Content);        
 * RemoveDuplicatedLinesByString
 * This function removes all duplicated lines of the given string.
 * @param     string
 * @param     bool
 * @return    string
function RemoveDuplicatedLinesByString($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 == '')
        // 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] = $CurrentLine;        
    // Sort the array
    // Return how many lines got removed
    return implode($NewLine, array_values($LineArray));    
Snippet Details

// 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, ';');

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Older comments:

George July 25, 2010 at 21:50
Hi this is my code: it takes e-mail address from flash form ahd Php write the address into a plan text file.
Can you help me to use the code you provide so the e-mails don't duplicate in the text.
Thanks in advance!


$file = fopen("mailing.txt", "a");
fwrite($file, "n" . $from);

#change the email address in the variable $adminaddress below to the email address you want
#the form to send to.

$adminaddress = "";
$sitename = "Vivre dans les Dignite";

#make sure your input field variable names in flash are the same as the field names below,
#leave out the dollar sign in flash.

mail("$adminaddress","Info Request",
"A customer at $sitename has made the following enquiryn
First Name: $name
Last Name: $lname
Town: $town
Telephone: $telno
Address: $address
Postal Code: $pcno
Email: $fromn
The visitor commented:

Logged Info :
Hostname: $ip
IP address: $REMOTE_ADDR
Date/Time: $date","FROM:$adminaddress");