- print_r: documentation ( source)
- array_walk_recursive: documentation ( source)
<?php
$arr = array(
Array('weight' => '317.51474856007','reps' => '10'),
Array('weight' => 50,'reps' => 10),
Array('reps' => 10),
Array('reps' => 10)
);
array_walk_recursive($arr, function($v, $k)use(&$count){if(array_key_exists($k, $count))$count[$k]++;else $count[$k]=1;}, $count=array());
print_r($count);