From mediawiki.org
Available from version 1.19 (Gerrit change 224373)
Enables debugging of server results
Define function:
public static function onMathRenderingResultRetrieved( $renderer, $jsonResult ) { ... }
Attach hook:
$wgHooks['MathRenderingResultRetrieved'][] = 'MyExtensionHooks::onMathRenderingResultRetrieved';
Called from:File(s): Math / MathLaTeXML.php, MathMathML.php
Function(s): doRender, processJsonResult

For more information about attaching hooks, see Manual:Hooks .
For examples of other extensions using this hook, see Category:MathRenderingResultRetrieved extensions.