Loop through array grouping indexes by value within that array (PHP) - php

Question

I wish to create a list of items from an array, grouped by a value within that array.
Take this array:
$people = array(
0 => array(
"Forename" => "Jim",
"Surname" => "Smith"
),
1 => array(
"Forename" => "Mike",
"Surname" => "Johnson"
),
2 => array(
"Forename" => "Kim",
"Surname" => "Smith"
),
3 => array(
"Forename" => "Paul",
"Surname" => "Jones"
)
);
Specifically I'd like to run a foreach on $people, grouping them by unique surname. i.e. the desired output would be:
<select>
<optgroup label="Smith">
<option>Jim</option>
<option>Kim</option>
</optgroup>
<optgroup label="Johnson">
<option>Mike</option>
</optgroup>
<optgroup label="Jones">
<option>Paul</option>
</optgroup>
</select>
I'm struggling to come up with anything vaguely efficient and the Google gods aren't watching over me today :( What's the best approach for such a use-case in PHP?

Answer 1

$surnames = array();
foreach($people as $person) {
$surnames[$person['surname']][] = $person;
}
This code stores all persons in an array grouped by their surnames.
The resulting array:
array(
'smith' => array(
0 => array(
"Forename" => "Jim",
"Surname" => "Smith"
),
1 => array(
"Forename" => "Kim",
"Surname" => "Smith"
)
),
'jones' => array(
0 => array(
"Forename" => "Paul",
"Surname" => "Jones"
)
)
)

Answer 2

I would do this way:
$grouped = array();
foreach ($people as $p){
if (!array_key_exist($p["Surname"], $grouped)){
$grouped[$p["Surname"]] = array();
}
$grouped[$p["Surname"]][] = $p;
}

Answer 3

I've added one more duplicate person:
....
4 => array
(
"Forename" => "Kim",
"Surname" => "Smith"
)
);
this is how you filter array :
$uniqueNames = array();
foreach($people as $person)
{
$uniqueNames[$person['Surname']][] = $person['Forename'];
}
if however you also need Forename to be unique, you can do it like this:
$uniqueNames = array_map
(
function($arrayItem)
{
if (is_array($arrayItem))
{
return array_unique($arrayItem);
}
}
, $uniqueNames
);
Also I've made some easy functions to generate html code:
function htmlSelect($name, $optionsData, $selectedItem = null)
{
$str = "\n<select name='$name' id='select-$name'>";
foreach ($optionsData as $k => $value_s)
{
if(is_array($value_s))
{
$str .= htmlOptgroup($k, $value_s);
}
else
{
$selected = ($selectedItem && $selectedItem == $k);
$str .= "\n\t".htmlOption($value_s, $k, $selected);
}
}
$str .= "\n</select>";
return $str;
}
function htmlOptgroup($label, $optionsData, $selectedItem = null)
{
$str = "\n\t<optgroup label='$label'>";
foreach ($optionsData as $k => $value)
{
$selected = ($selectedItem && $selectedItem == $k);
$str .= "\n\t\t".htmlOption($value, $k, $selected);
}
$str .= "\n\t</optgroup>";
return $str;
}
function htmlOption($display, $value, $selected = false)
{
$selectedStr = $selected ? " selected='selected'" : "" ;
return "<option$selectedStr value='$value'>$display</option>";
}
these functions can easily move to static class for html.
finally you call:
echo htmlSelect('unique-surnames', $uniqueNames);
I swear when I started there was no any answers :d