PHP group keys in array with multiple values - php

Question

I've got an array like this:
$sendemail= array(
'apple#yahoo.com' => '123456781234567',
'apple#yahoo.com' => '013881002296968',
'cherry#yahoo.com' => '3553220865206561',
'orange#yahoo.com' => '358805051217453',
'apple#yahoo.com' => '357998054217777',
'cherry#yahoo.com' => '013881002296968',
);
I would like to have an output like this:
'apple#yahoo.com' => 123456781234567, 013881002296968, 357998054217777
'cherry#yahoo.com' => 3553220865206561, 013881002296968
'orange#yahoo.com' => 358805051217453
to be able to use the keys as email address and the values as my email's buddy
$email= 'apple#yahoo.com';
$body= '123456781234567, 013881002296968, 357998054217777';
mail($email, 'Your codes', $body);
And the same for the other email addresses.
PLEASE NOTE that 2 keys might have the same values which is fine (e.g. apple#yahoo.com and cherry#yahoo.com have the same values; the value will be sent to both of them)
I used this 'for loop' but didn't work. first of all I cant group them based on email addresses, second of all the same values will not be assigned to the other email addresses; like '013881002296968' which should be shared with apple#yahoo.com and cherry#yahoo.com
$sendmail= array(
'123456781234567' => 'apple#yahoo.com',
'013881002296968' => 'apple#yahoo.com',
'3553220865206561' => 'cherry#yahoo.com',
'358805051217453' => 'orange#yahoo.com',
'357998054217777' => 'apple#yahoo.com',
'013881002296968' => 'cherry#yahoo.com',
);
$out = array();
foreach($sendmail as $key=>$value)
if(array_key_exists($value, $out)) {
$out[$value][] = $key;
}
else {
$out[$value] = array($key);
}
Output
array (
'apple#yahoo.com' =>
array (
0 => 123456781234567,
1 => 013881002296968,
2 => 357998054217777,
),
'cherry#yahoo.com' =>
array (
0 => 3553220865206561,
),
'orange#yahoo.com' =>
array (
0 => 358805051217453,
),
)

Answer 1

Here is an alternative to Kris' method that has less iterations, but more conditionals:
Input:
$sendmail= array(
'123456781234567' => 'apple#yahoo.com',
'013881002296968' => 'apple#yahoo.com',
'3553220865206561' => 'cherry#yahoo.com',
'358805051217453' => 'orange#yahoo.com',
'357998054217777' => 'apple#yahoo.com',
'013881002296968' => 'cherry#yahoo.com',
);
Method:
foreach($sendmail as $k=>$v){
if(!isset($out[$v])){$out[$v]='';} // initialize new element with empty string
$out[$v].=($out[$v]?',':'').$k; // concat the values with conditional comma
}
var_export($out);
Output:
array (
'apple#yahoo.com' => '123456781234567,357998054217777',
'cherry#yahoo.com' => '013881002296968,3553220865206561',
'orange#yahoo.com' => '358805051217453',
)

Answer 2

Use implode on the element of your result array. live demo
foreach($sendmail as $key=>$value) {
$out[$value][] = $key;
}
$out = array_map(function($v){return implode(',', $v);}, $out);