Ages ago, I wrote a MODx snippet called ChunkIf and I thought it was about time that I shared it with the MODx community. ChunkIf allows you to choose which of two chunks gets output, based on a template variable being set or not; its not big or clever but I find it useful and hopefully you might do, too.

The long form of the snippet call looks like this:

[[ChunkIf? &tv=`tvname` &trueChunk=`chunkname` &falseChunk=`chunkname`  &debug=`1|0` ]]

The parameters to the snippet call work like this:

&tv

This is the name of the template variable you want to test. The value of this variable will be checked and if it’s not empty or blank, &trueChunk will be output – otherwise &falseChunk will be.

&trueChunk

The name of the chunk who’s content you want output, in the event that your template variable (&tv) has a value.

&falseChunk

The name of the chunk who’s content you want output, if your template variable (&tv) is empty. If you omit this parameter, an empty string will be output if &tv is empty.

&debug

Set this to 1 to emit debugging comments into the HTML output; set it to 0 or leave it out to switch off.

There is a short version too:

[[ChunkIf? &tv=`tvname` ]]

The shorthand form attempts to output the contents of a chunk with the same name as &tv, if &tv is set, or an empty string. If there’s no chunk with the same name, it also returns an empty string.

This shorthand version is very handy for switching chunks on and off using a single variable. As chunks can contain other chunks and snippet calls, you can use this to switch sidebars, footers and other complex bits of layout on and off on a per page basis, with a simple checkbox template variable.

<?php
	/*
		Version: 0.2
		Date: 21/07/2008
		Description:
			<strong>0.2</strong> Outputs the contents of the chunk passed in
			$trueChunk if the template variable passed in $tv is set (i.e. has a value).
			Otherwise outputs the contents of the $falseChunk chunk. Expects $tv to be the
			name of the Template Variable to test, and $trueChunk & $falseChunk to be names
			of chunks.

		eg:

		[[ChunkIf? &tv=`tvname` &trueChunk=`chunkname` &falseChunk=`chunkname` ]]
			- Long version outputs $trueChunk if $tv has a value, otherwise
			outputs $falseChunk.
		[[ChunkIf? &tv=`tvname` &trueChunk=`chunkname` ]]
			- This short version outputs an empty string if $tv has no value.
		[[ChunkIf? &tv=`tvname` ]]
			- This very short version attempts to output the contents of a chunk
			 with the same name as $tv
		[[ChunkIf? &tv=`tvname` &debug=`1` ]]
			- Switches on debugging output - output's HTML comments for debugging.

	*/

	// get tv name
	$tv = isset( $tv ) ? $tv : '';

	// get current page ID
	$id = isset( $id )? $id: $modx -> documentObject['id'];

	// Get the value of $tv
	$tvarray = $modx -> getTemplateVarOutput( $tv, $id );
	$value = ''.trim($tvarray[$tv]);

	if ($debug) {
		$dtmp = '<!--';
		$dtmp .= 'tv: '.$tv.', ';
		$dtmp .=  'id: '.$id.', ';
		$dtmp .=  'value: '.$value;
		$dtmp .=  '-->';

		echo $dtmp;
	}

	// Decide which chunk to return.
	if ($value == '') {
		// get chunk to return if $tv has no value
		$falseChunk = isset( $falseChunk )? $modx -> getChunk( $falseChunk ): '';
		return $falseChunk;
	} else {
		// get chunk to return if $tv has a value
		if (isset( $trueChunk ))
		{
			$trueChunk = $modx -> getChunk( $trueChunk );
		} else {
			// Attempt to get the chunk with the same name as $tv
			$trueChunk = $modx -> getChunk( $tv );
		}
		return $trueChunk;
	}
?>