Find - n - replace

Hello all. I'm trying to set up a quick find and replace script. It's finding, and it's pasting what I want, but on the following line, I can't get it to replace. Can anyone help? #!/usr/local/bin/php -q <?php $fp = fopen( "./somefile.html","r+"); while ( !feof( $fp ) ) { $line = fgets( $fp, 4096 ); if ( eregi( "<td", $line ) ) { if ( eregi( "4[0-9]{2}", $line ) ) { $liner = eregi_replace( "4[0-9]{2}", "470", $line ); fputs( $fp, $liner, strlen( $liner ) ); } } } fclose( $fp ); ?> Can anyone tell me how I can back the fput up one line so it overwrites the result of the search? Thanks, John