How to search Array for multiple values in PHP?

Question 1

I need to get the keys from values that are duplicates. I tried to use array_search and that worked fine, BUT I only got the first value as a hit.

I need to get both keys from the duplicate values, in this case 0 and 2. The search result output as an array would be good.

Is there a PHP function to do this or do I need to write some multiple loops to do it?

$list[0][0] = "2009-09-09";
$list[0][1] = "2009-05-05";
$list[0][2] = "2009-09-09";
$list[1][0] = "first-paid";
$list[1][1] = "1";
$list[1][2] = "last-unpaid";

echo array_search("2009-09-09",$list[0]);

Question 2

You want array_keys with the search value

array_keys($list[0], "2009-09-09");

which will return an array of the keys with the specified value, in your case [0, 2]. If you want to find the duplicates as well, you can first make a pass with array_unique, then iterate over that array using array_keys on the original; anything which returns an array of length > 1 is a duplicate, and the result is the keys in which the duplicates are stored. Something like...

$uniqueKeys = array_unique($list[0])

foreach ($uniqueKeys as $uniqueKey)
{
  $v = array_keys($list[0], $uniqueKey);

  if (count($v) > 1)
  {
    foreach ($v as $key)
    {
      // Work with $list[0][$key]
    }

  }
}

Question 3

Code:

function search($array, $key, $value)
{
    $results = array();

    if (is_array($array)) {
        if (isset($array[$key]) && $array[$key] == $value) {
            $results[] = $array;
        }

        foreach ($array as $subarray) {
            $results = array_merge($results, search($subarray, $key, $value));
        }
    }

    return $results;
}

$arr = array(0 => array(id=>1,name=>"cat 1"),
             1 => array(id=>2,name=>"cat 2"),
             2 => array(id=>3,name=>"cat 1"));

print_r(search($arr, 'name', 'cat 1'));

Output:

Array
(
    [0] => Array
        (
            [id] => 1
            [name] => cat 1
        )

    [1] => Array
        (
            [id] => 3
            [name] => cat 1
        )

)

If efficiency is important you could write it so all the recursive calls store their results in the same temporary $results array rather than merging arrays together, like so:

function search($array, $key, $value)
{
    $results = array();
    search_r($array, $key, $value, $results);
    return $results;
}

function search_r($array, $key, $value, &$results)
{
    if (!is_array($array)) {
        return;
    }

    if (isset($array[$key]) && $array[$key] == $value) {
        $results[] = $array;
    }

    foreach ($array as $subarray) {
        search_r($subarray, $key, $value, $results);
    }
}

The key there is that search_r takes its fourth parameter by reference rather than by value; the ampersand & is crucial.

FYI: If you have an older version of PHP then you have to specify the pass-by-reference part in the call to search_r rather than in its declaration. That is, the last line becomes search_r($subarray, $key, $value, &$results).

Question 4

For the purpose of keeping individuals who may come across this answer from obtaining out-of-date information I have updated it in regards to the latest PSR autoloading standards. The original answer has been maintained for historical purposes and for those who are only interested in the PSR-0 autoloader.

Updated Answer

The PHP-FIG has officially deprecated the PSR-0 standard in favor of the alternative autoloader, PSR-4. Although the two are similar in some aspects they are also very different in others. (E.g.: the handling of underscores in class names.)

You may be thinking to yourself -- "I use PSR-0 now and it works fine." The truth of the matter is that PSR-0 will still work fine for certain projects. This is especially true when backwards compatibility with a package that doesn't use namespaces is concerned. PSR-0 is still a decent autoloading principle, but it has its own shortcomings.

Of course, if there is one thing that is a constant with programming, it is that code eventually changes and programming techniques continue to evolve. You can do yourself a favor today by preparing yourself for tomorrow. Therefore, if you are just starting a project or are trying to port a project to a newer version of PHP that can use namespaces, you should seriously consider using the PSR-4 autoloader.

It is also worth noting that if you are developing a project that does not use namespaces then PSR-4 does not apply to you. In this case PSR-0 or your own custom autoloader applies.

Original Answer

If you want to go with namespaces in your classes, then the PSR-0 route is a pretty good way to autoload. Basically your namespace represents you directory structure and classes can be loaded based on a convention.

If the PSR-0 method doesn't meet all your needs (or doesn't play nice with existing code) you can still add more functions with spl_autoload_register and PHP will go through them one by one in an attempt to load classes.

Example usage:

First thing is first, if you aren't familiar with namespaces in PHP then you will benefit from checking out the PHP manual on the subject. They can be a bit confusing at first, but their benefits are worth the initial confusion.

So I said that PSR-0 works by associating your namespaces with your directory structure. Let's use your directories for an example. You have in your root folder (wherever it may be) the following:

Project directory:  <- Let's call this directory "MyProject"
    Controllers:
       Main.php
       File.php
       About.php
    Libs:
       Main.php
       Front_controller.php
    Models:
       Index.php
       File.php
       Login.php
index.php <- Let's say this is your entry point file, this is where you will be autoloading stuff from.

Now let's take a look at your controller Main.php. Two things to keep in mind is that the class name needs to be the name of the file and the namespace for that class is the directory path to that file. So Main.php should look something like this:

<?php

namespace MyProjectControllers;

class Main {

    //Field vars, contructor, methods, etc. all go here.
    
}

?>

You would do the same thing for your your Login model

<?php

namespace MyProjectModels;

class Login {

    //Field vars, contructor, methods, etc. all go here.
    
}

?>

Now in your index.php file (out in the root directory - MyProject) you would make your call to the spl_autoload_register and give it the PSR-0 autoloader.

spl_autoload_register( function ($className) {
    $className = ltrim($className, '\');
    $fileName  = '';
    $namespace = '';
    if ($lastNsPos = strrpos($className, '\')) {
        $namespace = substr($className, 0, $lastNsPos);
        $className = substr($className, $lastNsPos + 1);
        $fileName  = str_replace('\', DIRECTORY_SEPARATOR, $namespace) . DIRECTORY_SEPARATOR;
    }
    $fileName .= str_replace('_', DIRECTORY_SEPARATOR, $className) . '.php';

    require $fileName;
});

//Now you can make your call to your objects without a bunch of include/require statements

$main = new MyProjectControllersMain();  //Instantiates your 'Main' controller
$login = new MyProjectModelsLogin();   //Instantiates your 'Login' model

Hopefully that helps make better sense of it, and again, if you don't want to use namespaces you can always just keep adding closures into the SPL autoload stack. You can have 10 different autoloaders in there if you want and PHP will go through them one by one (in the order you defined them) using each function to try and load a class. However, a couple convention based autoloaders is a bit cleaner and more of a preferred method. Also keep in mind that the autoloader translates both namespace separators and underscores _ as a directory separator. So your Front_controller.php would not autoload as you would expect.

Question 5

You can try foreach value test if contains strstr().

    foreach ($country as $n => $state)
    {
        if (strstr($state, 'USA'))
        {
            //found
            break;
        }
    }

Question 6

You have a couple of questions here, so I'll address them separately:

I need to store a number of selected items in one field in a database

My general rule is: don't. This is something which all but requires a second table (or third) with a foreign key. Sure, it may seem easier now, but what if the use case comes along where you need to actually query for those items individually? It also means that you have more options for lazy instantiation and you have a more consistent experience across multiple frameworks/languages. Further, you are less likely to have connection timeout issues (30,000 characters is a lot).

You mentioned that you were thinking about using ENUM. Are these values fixed? Do you know them ahead of time? If so this would be my structure:

Base table (what you have now):

| id primary_key sequence
| -- other columns here.

Items table:

| id primary_key sequence
| descript VARCHAR(30) UNIQUE

Map table:

| base_id  bigint
| items_id bigint

Map table would have foreign keys so base_id maps to Base table, and items_id would map to the items table.

And if you'd like an easy way to retrieve this from a DB, then create a view which does the joins. You can even create insert and update rules so that you're practically only dealing with one table.

What format should I use store the data?

If you have to do something like this, why not just use a character delineated string? It will take less processing power than a CSV, XML, or JSON, and it will be shorter.

What column type should I use store the data?

Personally, I would use TEXT. It does not sound like you'd gain much by making this a BLOB, and TEXT, in my experience, is easier to read if you're using some form of IDE.