print a header and sort by an array value

Question

I have an array containing possible values:

$auto_types = array(CHEVY, FORD, DODGE);

And I have have arrays that contain those values:

$my_cars = array(
  array("make" => "FORD", model => "Thunderbird", "year" => 1983),
  array("make" => "FORD", model => "Mustang", "year" => 1971),
  array("make" => "CHEVY", model => "Impala", "year" => 1995),
  array("make" => "DODGE", model => "Charger", "year" => 2015),
  array("make" => "CHEVY", model => "Corvette", "year" => 2011),
  array("make" => "CHEVY", model => "Camaro", "year" => 2012)
)

I want to return a list that supplies a header of each make, and then sorts each car by the Make. So the output would be:

CHEVY:
1995 Impala
2012 Corvette
2011 Camaro

DODGE:
2015 Charger

FORD:
1971 Mustang
1983 Thunderbird

I know I can run a foreach() loop and sort by make, but the key here is that I want a header for each make, instead of listing it for every car. Anyone have a good way to do this? -- Not sure if the first array is even needed, but it seemed like a good idea to create it at the time.

Answer 1

First you'll want to sort the array by make. You can do that with the help of array_multisort().

When you loop through your array for your list output, you can keep a variable that stores the make of the previous car. Then, whenever there's a new make, just print a header before the car's entry.

$ex_make = '';

foreach($my_cars as $car) {
    ...
    if ($car['make'] != $ex_make) {
        print_header($car['make']);
    }
    ...
    $ex_make = $car['make'];
}

You can make your life easier by grouping your cars by make into a multidimensional array. It'll spare you from the sorting process (and the grouping loops suggested in other answers). If you have lots more cars coming in, you'll want to consider using a database instead.

Answer 2

You don't need the first array. You can use one loop to group the cars by make:

foreach ($my_cars as $car) {
    $makes[$car['make']][] = $car;
}

If you want the makes to appear in alphabetical order, then you can ksort($makes).

Then loop over the makes and print the cars for each one.

foreach ($makes as $make => $cars) {
    echo "$make: ";                       // Header prints once
    foreach ($cars as $car) {
        echo "$car[model] $car[year] ";   // Multiple cars print after each header
    }
    echo '<br>';
}

Answer 3

<?php

$my_cars = array(
  array("make" => "FORD", "model" => "Thunderbird", "year" => 1983),
  array("make" => "FORD", "model" => "Mustang", "year" => 1971),
  array("make" => "CHEVY", "model" => "Impala", "year" => 1995),
  array("make" => "DODGE", "model" => "Charger", "year" => 2015),
  array("make" => "CHEVY", "model" => "Corvette", "year" => 2011),
  array("make" => "CHEVY", "model" => "Camaro", "year" => 2012)
);

// defining empty arrays for each models
$ford = [];
$chevy = [];
$dodge = [];

// loop through every car and push to the right array model
foreach($my_cars as $array) {
  if($array['make'] == "FORD") {
    array_push($ford, $array);
  } elseif($array['make'] == "CHEVY") {
    array_push($chevy, $array);
  } else {
    array_push($dodge, $array);
  }
}

// echo the result by looping inside each array model
foreach($dodge as $car) {
  echo $car['year'] . ':' . $car['model'] . '<br />';
}

echo '<br />';

foreach($ford as $car) {
  echo $car['year'] . ':' . $car['model'] . '<br />';
}

echo '<br />';

foreach($chevy as $car) {
  echo $car['year'] . ':' . $car['model'] . '<br />';
}

Answer 4

Nested Loop would be ideal here.

    <?php
        $auto_types = array("CHEVY", "FORD", "DODGE");
        $my_cars    = array(
            array("make" => "FORD",  "model" => "Thunderbird",  "year" => 1983),
            array("make" => "FORD",  "model" => "Mustang",      "year" => 1971),
            array("make" => "CHEVY", "model" => "Impala",       "year" => 1995),
            array("make" => "DODGE", "model" => "Charger",      "year" => 2015),
            array("make" => "CHEVY", "model" => "Corvette",     "year" => 2011),
            array("make" => "CHEVY", "model" => "Camaro",       "year" => 2012)
        );

        $arr = [];
        foreach($my_cars as $my_car){
            foreach($auto_types as $auto_type){
                if($make = array_search($auto_type, $my_car)){
                    $desc   = $my_car['make'] . " " . $my_car['year'] . " " . $my_car['model'];
                    if(!array_key_exists($auto_type, $arr)){
                        $arr[$auto_type] = $desc;
                    }else{
                        $arr[$auto_type] = $arr[$auto_type] .  "    " . $my_car['year'] . " " . $my_car['model'] . "";
                    }
                }
            }
        }
        ksort($arr);

        var_dump ($arr);
        // PRODUCES::           
        array (size=3)
          'CHEVY' => string 'CHEVY 1995 Impala    2011 Corvette    2012 Camaro' (length=49)
          'DODGE' => string 'DODGE 2015 Charger' (length=18)
          'FORD' => string 'FORD 1983 Thunderbird    1971 Mustang' (length=37)

        $output = implode("<br />", $arr);
        echo $output;

        // PRODUCES::
        CHEVY 1995 Impala 2011 Corvette 2012 Camaro
        DODGE 2015 Charger
        FORD 1983 Thunderbird 1971 Mustang

EFFECTIVE CODE

    <?php
        $arr = [];
        foreach($my_cars as $my_car){
            foreach($auto_types as $auto_type){
                if($make = array_search($auto_type, $my_car)){
                    $desc   = $my_car['make'] . " " . $my_car['year'] . " " . $my_car['model'];
                    if(!array_key_exists($auto_type, $arr)){
                        $arr[$auto_type] = $desc;
                    }else{
                        $arr[$auto_type] = $arr[$auto_type] .  "    " . $my_car['year'] . " " . $my_car['model'] . "";
                    }
                }
            }
        }
        ksort($arr);
        $output = implode("<br />", $arr);  //<== GET STRING VALUE...
        echo $output;