Grouping an array by a key in a foreach loop

Question

$result is an array that looks like this:

Array ( 
  [0] => stdClass Object (
    [Key_1] => a 
    [Key_2] => 10 
  )
  [1] => stdClass Object (
    [Key_1] => b
    [Key_2] => 10 
  ) 
  [2] => stdClass Object ( 
    [Key_1] => c
    [Key_2] => 20
   ) 
)

How can I echo $result in a foreach loop grouped by [Key_2] wrapped in a div like

<div class="new_Key_2">
  Key_2: 10
  ------------
  Key_1: a
  Key_1: b
</div>

<div class="new_Key_2">
  Key_2: 20
  ------------
  Key_1: c
</div>

I know how to open the div by checking if [Key_2] has changed, but not how to close it before a new [Key_2] comes along.

Matt Humphrey · Accepted Answer · 2012-10-12 14:28:07Z

3

PHP code that you need, you just need to play with it to match your HTML output needs.

<?php

$result = array();
foreach ($array as $object)
{
    $result[$object->key_2][] = $object->key_1;
}

foreach ($result as $key_2 => $keys)
{
    echo '<h1>'.$key_2.'</h1>';
    echo '<p>';
    echo implode('<br>', $keys);
    echo '</p>';
}

answered Oct 12, 2012 at 14:28

Matt Humphrey

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Comments

Baba · Accepted Answer · 2012-10-12 14:47:04Z

0

You can Group your array with array_reduce

$stdA = new stdClass();
$stdA->Key_1 = "a";
$stdA->Key_2 = 10;

$stdB = new stdClass();
$stdB->Key_1 = "b";
$stdB->Key_2 = 10;

$stdC = new stdClass();
$stdC->Key_1 = "a";
$stdC->Key_2 = 20;


# Rebuilding your array
$array = Array("0" => $stdA,"1" => $stdB,"2" => $stdC);


# Group Array
$array = array_reduce($array, function ($a, $b) {$a[$b->Key_2][] = $b;return $a;});

#Output Array
foreach ( $array as $key => $value ) {
    echo '<div class="new_Key_2">';
    echo "<h3> Key_2 : $key </h3>";
    foreach ( $value as $object ) 
        echo "<p>Key_1 : $object->Key_1</p>";
    echo '</div>';
}

Output

<div class="new_Key_2">
    <h3>Key_2 : 10</h3>
    <p>Key_1 : a</p>
    <p>Key_1 : b</p>
</div>
<div class="new_Key_2">
    <h3>Key_2 : 20</h3>
    <p>Key_1 : a</p>
</div>

answered Oct 12, 2012 at 14:47

Baba

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4 Comments

joko13 Over a year ago

Parse error: syntax error, unexpected T_FUNCTION in line $array = array_reduce($array, ...

Baba Over a year ago

What version of PHP are you using ??? See Live Demo : codepad.viper-7.com/xGiSXR

Pennywise83 Over a year ago

Hi, I don't understand why but with your code I receive an error "Parse error>: syntax error, unexpected T_FUNCTION in ..." relatively to the array_reduce function.

Baba Over a year ago

@Pennywise83 what version of PHP are you using ?

Nikolaos Dimopoulos · Accepted Answer · 2012-10-12 14:33:57Z

0

Assuming that your initial array is $my_array

// Generating a new array with the groupped results
$new_array = array();
foreach ($my_array as $element) 
{
    $new_array[$element->Key_2][] = $element->Key_1;
}

And then in your view layer you can echo each div/element in turn

<?php foreach ($new_array as $key => $items) { ?>

<div class="new_Key_2">
    Key_2 : <?php echo $key; ?><br />
    ---------------------------<br />
    <?php echo implode('<br />', $items); ?>
</div>

<?php } ?>

answered Oct 12, 2012 at 14:33

Nikolaos Dimopoulos

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Comments

JvdBerg · Accepted Answer · 2012-10-12 14:34:29Z

0

Just loop through the array of objects, and hold a separate group variable to the last group. No need to loop the array twice and generate a new array.

$group = false;
foreach($array as $object) {

  if($group !== false)
     echo '</div>';

  if($group != $object->Key_2) {
    echo '<div class="new_key_2">';
  }
  $group = $object->Key_2;
  // do stuff
}

if($group !== false)
  echo '</div>';

edited Oct 12, 2012 at 14:34

answered Oct 12, 2012 at 14:28

JvdBerg

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