How to delete a line from the file with php?

问题:

I have a file named $dir and a string named $line, I know that this string is a complete line of that file but I don't know its line number and I want to remove it from file, what should I do?

Is it possible to use awk?

回答1:

$contents = file_get_contents($dir);
$contents = str_replace($line, '', $contents);
file_put_contents($dir, $contents);

回答2:

Read the lines one by one, and write all but the matching line to another file. Then replace the original file.

回答3:

this will just look over every line and if it not what you want to delete, it gets pushed to an array that will get written back to the file. see this

 $DELETE = "the_line_you_want_to_delete";

 $data = file("./foo.txt");

 $out = array();

 foreach($data as $line) {
     if(trim($line) != $DELETE) {
         $out[] = $line;
     }
 }

 $fp = fopen("./foo.txt", "w+");
 flock($fp, LOCK_EX);
 foreach($out as $line) {
     fwrite($fp, $line);
 }
 flock($fp, LOCK_UN);
 fclose($fp);  

回答4:

Another approach is to read the file line by line until you find a match, then truncate the file to that point, and then append the rest of the lines.

回答5:

This is also good if you're looking for a substring (ID) in a line and want to replace the old line with the a new line.

Code:

$contents = file_get_contents($dir);
$new_contents= "";
if( strpos($contents, $id) !== false) { // if file contains ID
    $contents_array = preg_split("/\\r\\n|\\r|\\n/", $contents);
    foreach ($contents_array as &$record) {    // for each line
        if (strpos($record, $id) !== false) { // if we have found the correct line
            pass; // we've found the line to delete - so don't add it to the new contents.
        }else{
            $new_contents .= $record . "\r"; // not the correct line, so we keep it
        }
    }
    file_put_contents($dir, $new_contents); // save the records to the file
    echo json_encode("Successfully updated record!");
}
else{
    echo json_encode("failed - user ID ". $id ." doesn't exist!");
}

Example:

input: "123,student"

Old file:

ID,occupation

123,student

124,brick layer

Running the code will change file to:

New file:

ID,occupation

124,brick layer

回答6:

It can be solved without the use of awk:

function remove_line($file, $remove) {
    $lines = file($file, FILE_IGNORE_NEW_LINES);
    foreach($lines as $key => $line) {
        if($line === $remove) unset($lines[$key]);
    }
    $data = implode(PHP_EOL, $lines);
    file_put_contents($file, $data);
}

回答7:

Like this:

file_put_contents($filename, str_replace($line . "\r\n", "", file_get_contents($filename)));

回答8:

I think the best way to work with files is to edit them as strings.

First, get all lines of the file (the following codes can be compressed):

$file = @fopen($dir, 'r'); # As you said, $dir is your filename
if ($file) { # Ending bracket is at the end
    if (filesize($dir)) { # Checks whether the file size is not zero (we know file exists)
        $fileContent = fread($file, filesize($dir)); # Reads all of the file
        fclose($file);
    } else {
        // File is empty
        exit; # Stops the execution (also you can throw an exception)
    }
    $fileLineByLine = explode(PHP_EOL, $fileContent); # Divides the file line by line

Here, you can perform your search:

    $key = false; # By default, your string $line is not in the file (false)
    foreach ($fileLineByLine as $lineNumber => $thisLine)
        if ($thisLine === $line)
            $key = $lineNumber; # If $line found in file, set $key to this line number

Simply, you can remove line $key + 1:

    if ($key !== false) # If string $line found in the file
        unset($fileLineByLine[$key]); # Remove line $key + 1 (e.g. $key = 2, line 3)

At last, you must save your changes to the file:

    $newFileContent = implode(PHP_EOL, $fileLineByLine); # Joins the lines together
    $file = fopen($dir, "w"); # Clears the file
    if ($file) {
        fwrite($file, $newFileContent); # Saves new content
        fclose($file);
    }
} # Ends 'if ($file) {' above

Also you can set above code as a function.

Notes:

• $line must not have new line characters like \n. You must remove them:

  $line = str_replace(PHP_EOL, '', $line);
  

• Don't use

  $fileLineByLine[$key] = "";
  

  instead of

  unset($fileLineByLine[$key]);
  

  because the first case doesn't remove the line, it just clears the line (and an unwanted empty line will remain). In that case, implode() adds a new line also for $fileLineByLine[$key] which is empty; otherwise if you unset a variable, it will unavailable (and implode() can not find it).