Wicked Cool PHP

#40: Rearranging a Table

Let's look at several utilities that use regular expressions. For a more complex example, let's say that you have a bunch of entries in an HTML table that looks like this:

<tr><td>last_name, first_name</td>
<td>address</td>
<td>phone number</td>
</tr>

Now assume that your boss just can't leave well enough alone and insists that you change it to this format:

<tr><td>first_name</td>
<td>last_name</td>
<td>address</td>
<td>phone number</td>
</tr>

You can do this in one fell swoop with backreferencing:

$table = preg_replace('/<td>([^<]*),\s*([^<]*)<\/td>/',
                      '<td>$1</td>' . "\n" . '<td>$2</td>',
                      $/table);

A bit of explanation is necessary. I split the arguments into three lines because they're easier to read that way. Notice that ...