Perl-style regular expressions( preg_replace_callback)

• preg_replace_callback() - 
                                          With preg_replace(), the function itself is responsible for handling the
replacement procedure. With preg_replace_callback(), the handling of the replacement procedure is
handed off to another function to take care of. The syntax is identical to preg_replace() except where
the replacement text would be located, a function name is present. This function is responsible for
handling any of the replacement changes to the text that matches the pattern searched.

<?php
$text = "Dear <pnm>S</pnm>Ortiz,<br>&nbsp;&nbsp;&nbsp;&nbsp;I
would like to thank you and <pnf>F</pnf>Picard for taking the
time in talking to me today. Please feel free to contact me if
you have any additional
questions.<br>Sincerely,<br><pnm>E</pnm>Bob Riker";
function proper_name_m($matches) {
$titles = array(
'E' => 'Mr. ',
'S' => 'Sr. ',
'F' => 'M ');
if (isset($titles[$matches[1]])) {
return $titles[$matches[1]];
} else {
return $matches[1];
}
}
function proper_name_f($matches) {
$titles = array(
'E' => 'Ms. ',
'S' => 'Sra. ',
'F' => 'Mme ');
if (isset($titles[$matches[1]])) {
return $titles[$matches[1]];
} else {
return $matches[1];
}
}
$new_text = preg_replace_callback("/<pnm>(.*)<\/pnm>/U",
'proper_name_m', $text);
$final_text = preg_replace_callback("/<pnf>(.*)<\/pnf>/U",
'proper_name_f', $new_text);
print $final_text;
?>

In the code presented above, a letter (which looks like a follow-up to a sales or interview meeting) has
been written. The user did not know the proper titles to use with the names, so they were taught to
place 'E' for English titles, 'S' for Spanish titles and 'F' for French titles. In addition, because of the
need to address both genders, they were also taught to identify the gender in the tags used:
<pnm>$language_code</pnm> for male and <pnf>$language_code</pnf> for female. The function
proper_name_m handles the replacement for the <pnm> tags and proper_name_f handles the
<pnf> tags. The first preg_replace_callback function handles the changing of the male titles
and then places the new text into the variable $new_text. The second
preg_replace_callback function handles the changing of the female titles and then finalizes
the text by placing the replaced contents in the variable $final_text.