Recursive functions in PHP
DanI thought that i should touch quickly on recursion as it is something that is needed for the below tutorial on creating a conversion script for Wordpress to Joomla
Recursive functions, are functions that call upon themselves repeatedly, in the example in the previous post the function updateCategory is a recursive function
function updateCategory($category, $newParentID) { global $db, $jb, $wp_prefix, $j_prefix; $children = $db->get_results("SELECT t.term_id as term_id, t.name as tname, t.slug as tslug, tt.description as description, tt.parent as parent FROM ".$wp_prefix."terms AS t INNER JOIN ".$wp_prefix."term_taxonomy AS tt ON t.term_id = tt.term_id WHERE tt.taxonomy IN ('category') and parent=".$category." ORDER BY t.name"); foreach($children as $child) { updateCategory($child->term_id, $newParentID); //Check if we are insterting into 1.5 or 1.0.x if($j_version=='1.5') { //Insert the latest category $jb->query("insert into ".$j_prefix."categories (title, alias, section, description, published) Values('".$child->tname."', '".$child->tslug."', '".$newParentID."', '".$child->description."', 1)"); } else { $jb->query("insert into ".$j_prefix."categories (title, name, section, description, published) Values('".$child->tname."', '".$child->tslug."', '".$newParentID."', '".$child->description."', 1)"); } // // Insert into our temp storage/reference table // $jb->query("insert into jos_wp_category_map (wp_cat_id, jos_cat_id, jos_sec_id) values(".$child->term_id.", ".$jb->insert_id.", ".$newParentID.")"); } } |
This function uses a recordset of data from the database, it then goes through each of the categories, sub-categories and inserts them in the database in a new level to it’s previous position, the function then calls itself again to check if the current record has children records.
This is a classic example of why recursion is useful and whilst not perfect coding, it does show the usefulness when you need to run a function for deep levels of information and in particular when you do not know how deep you need to go.
So to re-iterate, a recursive function simply calls itself multiple times.
I hope this helps and I hope you find new useful ways to use this, once learning recursive functions, it adds a whole new level to your coding and can cut the amount of lines of code you need to write in half.
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Currently working as a Technical Support Manager, I have some 5+ years experience as a PHP coder, and am here to share my experiences and ideas with you all. Whilst I no longer code full time, I often write snippets to help with day to day work, that I am sure you will find useful.
