You want to change a file without using a temporary file to hold the changes.
Read the file with file_get_contents(), make the changes, and rewrite the file with file_put_contents():
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$contents = file_get_contents('pickles.txt'); $contents = strtoupper($contents); file_put_contents('pickles.txt', $contents); |
This example turns text emphasized with asterisks or slashes into text with HTML <b> or <i> tags:
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$contents = file_get_contents('message.txt'); // convert *word* to <b>word</b> $contents = preg_replace('@\*(.*?)\*@i','<b>$1</b>',$contents); // convert /word/ to <i>word</i> $contents = preg_replace('@/(.*?)/@i','<i>$1</i>',$contents); file_put_contents('message.txt', $contents); |
Because adding HTML tags makes the file grow, the entire file has to be read into memory and then processed.
If the changes to a file make each line shrink (or stay the same size), the file can be processed line by line, saving memory.
For example, this converts text marked with <b> and <i> to text marked with asterisks and slashes:
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$fh = fopen('message.txt','r+') or die($php_errormsg); // figure out how many bytes to read $bytes_to_read = filesize('message.txt'); // initialize variables that hold file positions $next_read = $last_write = 0; // keep going while there are still bytes to read while ($next_read < $bytes_to_read) { /* move to the position of the next read, read a line, and save * the position of the next read */ fseek($fh,$next_read); $s = fgets($fh) or die($php_errormsg); $next_read = ftell($fh); // convert <b>word</b> to *word* $s = preg_replace('@<b[^>]*>(.*?)</b>@i','*$1*',$s); // convert <i>word</i> to /word/ $s = preg_replace('@<i[^>]*>(.*?)</i>@i','/$1/',$s); /* move to the position where the last write ended, write the * converted line, and save the position for the next write */ fseek($fh,$last_write); if (-1 == fwrite($fh,$s)) { die($php_errormsg); } $last_write = ftell($fh); } // truncate the file length to what we've already written ftruncate($fh,$last_write) or die($php_errormsg); // close the file fclose($fh) or die($php_errormsg); |
