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When Developing Snippets with Functions

  • sottwell Reply #1, 18 years, 5 months ago
    When writing a snippet (or TV or anything else, for that matter) and you write a function, make sure to enclose the function definition in a conditional. For example, a function in a snippet named MySnippet could have:

    if(!function_exists(MSmyFunction)) {
  function MSmyFunction() {
 ...
  } // end MSmyFunction
} // end function_exists


    If somebody wants to call your snippet more than once on the same page, or in a template, now they can. Otherwise, if a function is already defined by the first use of the snippet, PHP will throw an error when it’s defined again in the second use of the function.

    Also, it’s a good idea to somehow use your snippet name in all of your function names so there isn’t as much chance of somebody else’s snippet having a function of the same name that could cause a conflict.
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    • Ryan Thrash Reply #2, 18 years, 4 months ago
      Very good point Susan... I did just that recently. I had to add a bit more as follows (the !function_exists(function-name) technique resulted in a function already declared error when used twice on one page):

      global $MemberCheck_defined;

if (!isset ($MemberCheck_defined)) {

	function MemeberCheck($groups,$chunk) {
		global $modx;
		
		$check = $modx->isMemberOfWebGroup($groups);
		... do more stuff here ...		
		$o = ...
		
		return $o;
	}
	$MemberCheck_defined = true;
}

return MemeberCheck($groups,$chunk);


      This is also the way that DropMenu uses to be reused on the same page.

      Thanks for the tip!
        Ryan Thrash, MODX Co-Founder
        Follow me on Twitter at @rthrash or catch my occasional unofficial thoughts at thrash.me
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        qaraqter Reply #3, 8 years, 11 months ago
        Amazing.. 9 years later, and this is still saving lives smiley Thank you Susan!
        • sottwell Reply #4, 8 years, 11 months ago
          One other major function-in-snippets tip is that you need to explicitly declare $modx as global, otherwise your function won't be able to access any of the API functions or MODX properties.
            Studying MODX in the desert - http://sottwell.com
            Tips and Tricks from the MODX Forums and Slack Channels - http://modxcookbook.com
            Join the Slack Community - http://modx.org
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            Jeff Miranda Reply #5, 8 years, 3 months ago
            If I read this earlier it would've saved me 30 minutes of "WTF?!"

            Thanks for this Susan!
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              BobRay Reply #6, 8 years, 3 months ago
              Still an excellent tip, but the function name should be in quotes:

              if(!function_exists('MSmyFunction')) {



              Otherwise, PHP will throw this warning:

              PHP notice: Use of undefined constant MSmyFunction

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