How do I use PHP preg_replace_callback?

April 4, 2012

I’m working on a project that sends transactional emails from templates using variables in the %%varname%% format, but defines variables in another table as a lookup value, or query. So, I needed to match strings of type %%varname%% which screams regular expressions, but also needed varname to look up what to replace it with. So, instead of using multiple functions, I was able to do this with a callback and preg_replace_callback.

<?php
$string = "A complicated gentleman allow me to present,
Of all %%asdf%% the arts and faculties the terse embodiment,
He's a great arithmetician who can demonstrate with ease %%name%%
That two and two are three, or five, or anything you please;
An eminent Logician who can make it clear to you
That black is white – when looked at from the proper point of view;
A marvelous Philologist who'll undertake to show %%asdf%%
That 'yes' is but another and a neater form of 'no'.";

echo preg_replace_callback('(%%.*%%)', 
	create_function(
	    '$matches',
	    'return getValue($matches)'
	),
	$string
);

function getValue($var) { 
	return toupper(str_replace('%%', '', $var));
}

/* Outputs:
A complicated gentleman allow me to present,
Of all ASDF the arts and faculties the terse embodiment,
He's a great arithmetician who can demonstrate with ease NAME
That two and two are three, or five, or anything you please;
An eminent Logician who can make it clear to you
That black is white – when looked at from the proper point of view;
A marvelous Philologist who'll undertake to show ASDF
That 'yes' is but another and a neater form of 'no'.
*/

I use the function getValue to query the database and get the value of the variable. This function is pretty slick; now, PHP just needs to support callbacks that aren’t created as strings and we’ll be all set.

Author

Stay in Touch!

Stay in Touch!
Solutions Architecture

browse through our blog articles

Blog Archive