new_get_page_children.php

<?php

class FakePost {
    public function __construct($ID, $post_parent) {
        $this->ID = $ID;
        $this->post_parent = $post_parent;
    }
}


function get_post_children($page_id, $pages) {
    $posts_hash = array();
    $children_hash = array();

    // build a hash of ID -> children
    foreach ( (array) $pages as $page ) {
        $posts_hash[$page->ID] = $page;
        if ( !array_key_exists( $page->post_parent, $children_hash ) ) {
            $children_hash[$page->post_parent] = [$page->ID];
        } else {
            $children_hash[$page->post_parent][] = $page->ID;
        }
    }

    if( array_key_exists( $page_id, $children_hash ) ) {
        $pages = array();
        $to_look = array_reverse( $children_hash[$page_id] );
        // while we still have posts
        while ( $to_look ) {
            $id = array_pop( $to_look );
            $pages[] = $posts_hash[$id];
            if ( array_key_exists( $id, $children_hash ) ) {
                foreach( array_reverse( $children_hash[$id] ) as $child ) {
                    $to_look[] = $child;
                }
            }
        }
        return $pages;
    } else {
        return array();
    }
}

function ordered_pages($ids, $pages_hash, $children_hash) {
    $pages = [];
    foreach ($ids as $root) {
        $pages[] = $pages_hash[$root];
        if(array_key_exists($root, $children_hash)) {
            $op = ordered_pages($children_hash[$root], $pages_hash, $children_hash);
            foreach($op as $oi){
                $pages[] = $oi;
            }
        }
    }
    return $pages;
}

function new_get_page_children($page_id, $pages) {
    $pages_hash = array();
    $children_hash = array();
    foreach ( (array) $pages as $page ){
        $pages_hash[$page->ID] = $page;
        if (!array_key_exists($page->post_parent, $children_hash)) {
            $children_hash[$page->post_parent] = [$page->ID];
        } else {
            $children_hash[$page->post_parent][] = $page->ID;
        }
    }
    if(array_key_exists($page_id, $children_hash))
        return ordered_pages($children_hash[$page_id], $pages_hash, $children_hash);
    else
        return [];
}

function old_get_page_children($page_id, $pages) {
    $page_list = array();
    foreach ( (array) $pages as $page ) {
        if ( $page->post_parent == $page_id ) {
            $page_list[] = $page;
            if ( $children = old_get_page_children($page->ID, $pages) ) {
                $page_list = array_merge($page_list, $children);
            }
        }
    }
    return $page_list;
}

function tests() {
    $pages = [];
    $pages[] = new FakePost(1, 0);
    $pages[] = new FakePost(2, 0);
    $pages[] = new FakePost(3, 2);
    $pages[] = new FakePost(4, 2);
    $pages[] = new FakePost(5, 0);
    for ($i=6; $i < 1000; $i++) {
        $pages[] = new FakePost($i, rand(0, $i-1));
    }
    $max_depth = 50;
    for ($i=1000; $i < (1000 + $max_depth); $i++) {
        $pages[] = new FakePost($i, $i-1);
    }
    for ($i=(1000 + $max_depth); $i < 2000; $i++) {
        $pages[] = new FakePost($i, 5);
    }
    for ($i=2000; $i < 4000; $i++) {
        $pages[] = new FakePost($i, 1);
    }

    for ($i=0; $i < 8; $i++) {
        $time = [];
        $r = [];

        $time_start = microtime(true);
        $r[] = new_get_page_children($i, $pages);
        $time[] = (int) ((microtime(true) - $time_start) * 1000);

        $time_start = microtime(true);
        $r[] = get_post_children($i, $pages);
        $time[] = (int) ((microtime(true) - $time_start) * 1000);

        $time_start = microtime(true);
        $r[] = old_get_page_children($i, $pages);
        $time[] = (int) ((microtime(true) - $time_start) * 1000);

        echo ((($r[0] == $r[2]) && ($r[1]== $r[2]))?'Equal':'Different' );
        echo " $time[0] ms (new), $time[1] ms (post_children), $time[2] ms (old)\n";
    }
}

tests();