file/array manipulation

Hello I'm trying to manipulate a text(.csv) file using php. I've read the file and can print each line, but I need to write where column A is missing ColumnA ColumnB R ABC company ABC company ABC company ABC company O XYZ company XYZ company XYZ company XYZ company What I need to do is write a while loop (I think) to interate through the lines and populate ColumnA while ColumnB equals $var (ABC company then XYZ company), so that I end up with: ColumnA ColumnB R ABC company R ABC company R ABC company R ABC company O XYZ company O XYZ company O XYZ company O XYZ company Is this possible. What I've got so far to print out the file: $lines = file('test2.csv'); // Loop through our array, and show line and numbers too. foreach ($lines as $line_num => $line) { echo "Line #<b>{$line_num}</b> : " . $line . "<br />\n"; } Thanks in advance