Count the number of numeric keys in an array - php

Question

I'm using PHP 5.6, and I have the following array:
Array (
[0] => Array (
[id] => 1
[name] => James
)
[1] => Array (
[id] => 2
[name] => Tim
[children] => Array (
[0] => Array (
[id] => 4
[name] => Sam
)
[1] => Array (
[id] => 5
[name] => Florence
)
)
)
[2] => Array (
[id] => 3
[name] => Stephen
)
)
I'm trying to find a neat and fast way to count the number of people, which is the same as counting the number of numeric keys, which should be 5.
echo count($myarray); // 3 (only first level)
echo count($myarray, COUNT_RECURSIVE); // 16 (every key/value)
Is there a good way to do this with built-in PHP functions, or do I need to traverse the whole multidimensional array and count them manually..?
EDIT My array could end up being 1,000+ people (or more), with many many levels (an unknown number of levels).

Answer 1

It is important to note that, even if there were a PHP built-in (such as count($myarray, COUNT_RECURSIVE_NUMERIC);) internally, it would still be traversing the whole array, recursively. If you are worried about Out Of Memory errors, try pass-by-reference, which will not copy the array or the array items:
define('COUNT_RECURSIVE', 1);
function count_numeric_keys(&$array, $flags = 0) {
$count = 0;
foreach ($array as $key => $value) {
$count += (int) (is_numeric($key));
if ($flags & COUNT_RECURSIVE && is_array($value)) {
$count += count_numeric_keys($value, $flags);
}
}
return (int) $count;
}
$count = count_numeric_keys($array, COUNT_RECURSIVE);
Mayhaps?
Comparison with non-pass-by-reference, type-hint, and small benchmark:
define('COUNT_RECURSIVE', 1);
function count_numeric_keys(Array &$array, $flags = 0) {
$count = 0;
foreach ($array as $key => $value) {
$count += (int) (is_numeric($key));
if ($flags & COUNT_RECURSIVE && is_array($value)) {
$count += count_numeric_keys($value, $flags);
}
}
return (int) $count;
}
function count_numeric_keys_np(Array $array, $flags = 0) {
$count = 0;
foreach ($array as $key => $value) {
$count += (int) (is_numeric($key));
if ($flags & COUNT_RECURSIVE && is_array($value)) {
$count += count_numeric_keys_np($value, $flags);
}
}
return (int) $count;
}
$tpl_array = array(
1=>"one",
"two"=>"two",
3=>array(
1=>1,
"two"=>2
)
);
// Fill the array with both numeric and non-numeric
$array = array();
for($i = 1000; $i > 0; $i--) {
$array[] = $tpl_array;
}
for($i = 1000; $i > 0; $i--) {
$array["not a number $i"] = $tpl_array;
}
echo "Pre Memory: ".memory_get_usage(TRUE).PHP_EOL;
echo "Count: ".count_numeric_keys($array, COUNT_RECURSIVE).PHP_EOL;
echo "Reference Memory: ".memory_get_usage(TRUE)." current, ".memory_get_peak_usage(TRUE)." peak.\n";
count_numeric_keys_np($array, COUNT_RECURSIVE);
echo "No-Reference Memory: ".memory_get_usage(TRUE)." current, ".memory_get_peak_usage(TRUE)." peak.\n";
View it on IDEONE here.
ODDLY, having a reference on $value, like foreach($array as $key => &value) {} actually increased memory usage. Bizarre...

Answer 2

I just created this recursive function to do this for ya :P
function countNumericKeys($array)
{
$count = 0;
foreach ($array as $key => $value)
{
if (is_numeric($key))
{
$count ++;
}
if (is_array($value))
{
$count += countNumericKeys($value);
}
}
return $count;
}
// Test it!
$array = [
1=>"one",
"two"=>"two",
3=>[
1=>1,
"two"=>2
]
];
print countNumericKeys($array); // Output: 3, correct (in this case at least)!
Shortened the code so it uses ternary operators instead of the ifs that it was :P
function simpleCountNumericKeys($array)
{
$count = 0;
foreach ($array as $key => $value)
{
$count += is_numeric($key) ? 1 : 0;
$count += is_array($value) ? simpleCountNumericKeys($value) : 0;
}
return $count;
}
TEST USING array_keys -- only gets the top level keys of the array
function countArrayKeysNumeric($array)
{
$count = 0;
$keys = array_keys($array);
foreach ($keys as $key) $count += is_numeric($key) ? 1 :0;
return $count;
}
$array = [
1=>"one",
"two"=>"two",
3=>[
1=>1,
"two"=>2
]
];
print countArrayKeysNumeric($array);
Prints 2... :(