我如何有效地运行一个不会在 wamp 环境中永远执行的 PHP 脚本......？

Question

I've made a script that pretty much loads a huge array of objects from a mysql database, and then loads a huge (but smaller) list of objects from the same mysql database.

I want to iterate over each list to check for irregular behaviour, using PHP. BUT everytime I run the script it takes forever to execute (so far I haven't seen it complete). Is there any optimizations I can make so it doesn't take this long to execute...? There's roughly 64150 entries in the first list, and about 1748 entries in the second list.

This is what the code generally looks like in pseudo code.

// an array of size 64000 containing objects in the form of {"id": 1, "unique_id": "kqiweyu21a)_"}
$items_list = [];

// an array of size 5000 containing objects in the form of {"inventory: "a long string that might have the unique_id", "name": "SomeName", id": 1};
$user_list = [];

Up until this point the results are instant... But when I do this it takes forever to execute, seems like it never ends...

foreach($items_list as $item)
{
    foreach($user_list as $user)
    {
        if(strpos($user["inventory"], $item["unique_id"]) !== false)
        {
            echo("Found a version of the item");
        }
    }
}

Note that the echo should rarely happen.... The issue isn't with MySQL as the $items_list and $user_list array populate almost instantly.. It only starts to take forever when I try to iterate over the lists...

Answer 1

With 130M iterations, adding a break will help somehow despite it rarely happens...

foreach($items_list as $item)
{
    foreach($user_list as $user)
    {
        if(strpos($user["inventory"], $item["unique_id"])){
            echo("Found a version of the item");
            break;
        }
    }
}

alternate solutions 1 with PHP 5.6: You could also use PTHREADS and split your big array in chunks to pool them into threads... with break, this will certainly improve it.

alternate solutions 2: use PHP7, the performances improvements regarding arrays manipulations and loop is BIG.

Also try to sort you arrays before the loop. depends on what you are looking at but very oftenly, sorting arrays before will limit a much as possible the loop time if the condition is found.

Answer 2

Your example is almost impossible to reproduce. You need to provide an example that can be replicated ie the two loops as given if only accessing an array will complete extremely quickly ie 1 - 2 seconds. This means that either the string your searching is kilobytes or larger (not provided in question) or something else is happening ie a database access or something like that while the loops are running.

Answer 3

You can let SQL do the searching for you. Since you don't share the columns you need I'll only pull the ones I see.

SELECT i.unique_id, u.inventory
FROM items i, users u
WHERE LOCATE(i.unique_id, u inventory)