How to get the label in the result of an array - php

Question

The following code works as expected to get the number of patients per age group.
It also gets the highest (or most common) age group.
$count_0_19 = 0;
$count_20_29 = 0;
$count_30_39 = 0;
$count_40_49 = 0;
$count_50_59 = 0;
$count_above_60 = 0;
$curr_year = date('Y');
$sql= "SELECT pt_dob FROM ptlist WHERE mid=$userID";
$stmt = $pdo->query($sql);
$row = $stmt->fetch(PDO::FETCH_ASSOC);
$result = $pdo->query($sql);
$pt_dob = $row[ 'pt_dob' ];
while($row = $result->fetch(PDO::FETCH_ASSOC)) {
$pt_dob = explode('-', $row['pt_dob']);
$year = $pt_dob[0];
$month = $pt_dob[1];
$day = $pt_dob
$temp = abs($curr_year - $year);
if($temp >= 0 && $temp <= 19) {
$count_0_19++;
}
elseif($temp >= 20 && $temp <= 29) {
$count_20_29++;
}
elseif($temp >= 30 && $temp <= 39) {
$count_30_39++;
}
elseif($temp >= 40 && $temp <= 49) {
$count_40_49++;
}
elseif($temp >= 50 && $temp <= 59) {
$count_50_59++;
}
else {
$count_above_60++;
}
}
echo '0-19: '.$count_0_19.'<br>';
echo '20-29: '.$count_20_29.'<br>';
echo '30-39: '.$count_30_39.'<br>';
echo '40-49: '.$count_40_49.'<br>'; // example output is > 40-49: 7 (i.e. 7 patients in age group 40-49)
echo '50-59: '.$count_50_59.'<br>';
echo '60+: '.$count_above_60.'<br>';
// getting highest value
$a = array($count_0_19, $count_20_29, $count_30_39, $count_40_49, $count_50_59, $count_above_60);
$res = 0;
foreach($a as $v) {
if($res < $v)
$res = $v;
}
echo $res;
^^ This tells me that e.g. 9 patients are in the 30-39 age group - i.e. the highest number of patients are in this age group.
But $res gives me only the number (e.g. 9).
What I am asking your help with is to get $res to give me the text(or label) "30-39", instead of the number 9.
Please help.

Answer 1

continue from comment... you need to store $key into a variable.
$a = array('0-19'=>$count_0_19, '20-29'=>$count_20_29, '30-39'=>$count_30_39, '40-49'=>$count_40_49, '50-59'=>$count_50_59, '60+'=>$count_above_60);
$res = 0;
$label = '';
foreach($a as $key => $v) {
if($res < $v){
$res = $v;
$label = $key; //get label from key and store in a variable
}
}
echo 'label = '.$label . ' , Number = '.$res;

Answer 2

You can archived this by creating the array of labels and then incrementing it according and then find the greatest value form the $label array to get the key.
$label = [
"0_19" => 0,
"20_29" => 0,
"30_39" => 0,
"40_49" => 0,
"50_59" => 0,
"above_60" => 0,
];
while ($row4 = $result4->fetch(PDO::FETCH_ASSOC)) {
$pt_dob = explode('-', $row4['pt_dob']);
$year = $pt_dob[0];
$month = $pt_dob[1];
$day = $pt_dob$temp = abs($curr_year - $year);
if ($temp >= 0 && $temp <= 19) {
$label['0_19'] = $label['0_19'] +1;
}
elseif ($temp >= 20 && $temp <= 29) {
$label['20_29'] = $label['20_29'] +1;
}
elseif ($temp >= 30 && $temp <= 39) {
$label['30_39'] = $label['30_39']+1;
}
elseif ($temp >= 40 && $temp <= 49) {
$label['40_49'] = $label['40_49'] +1;
}
elseif ($temp >= 50 && $temp <= 59) {
$label['50_59'] = $label['50_59']+1;
}
else {
$label['above_60']= $label['above_60']+1;
}
}
echo $maxs = array_keys($label, max($label));
echo "<br/>";
foreach($label as $k => $v);
echo "key $k count $v <br/>";