how to replace a particular line in a text file using php?

Question

how to replace a particular row using php. I dont know the line number. I want to replace a line containing a particular word.

Answer 1

One approach that you can use on smaller files that can fit into your memory twice:

$data = file('myfile'); // reads an array of lines function replace_a_line($data) {    if (stristr($data, 'certain word')) {      return "replacement line!\n";    }    return $data; } $data = array_map('replace_a_line',$data); file_put_contents('myfile', implode('', $data)); 

A quick note, PHP > 5.3.0 supports lambda functions so you can remove the named function declaration and shorten the map to:

$data = array_map(function($data) {   return stristr($data,'certain word') ? "replacement line\n" : $data; }, $data); 

You could theoretically make this a single (harder to follow) php statement:

file_put_contents('myfile', implode('',    array_map(function($data) {     return stristr($data,'certain word') ? "replacement line\n" : $data;   }, file('myfile')) )); 

Another (less memory intensive) approach that you should use for larger files:

$reading = fopen('myfile', 'r'); $writing = fopen('myfile.tmp', 'w');  $replaced = false;  while (!feof($reading)) {   $line = fgets($reading);   if (stristr($line,'certain word')) {     $line = "replacement line!\n";     $replaced = true;   }   fputs($writing, $line); } fclose($reading); fclose($writing); // might as well not overwrite the file if we didn't replace anything if ($replaced)  {   rename('myfile.tmp', 'myfile'); } else {   unlink('myfile.tmp'); }