Tips on using PHP arrays

$arr = array(
 array('id'=>1,'cid' => 1, 'country' => 'China',' province'=>'Hunan'),
 array('id'=>2,'cid' => 1, 'country' => 'China','province'=>'Hunan'),
 array('id'=>3,'cid' => 3, 'country' => 'Japan','province'=>'Nagoya'),
 array('id'=>4 ,'cid' => 3, 'country' => 'Japan','province'=>'Tokyo'),
 array('id'=>5,'cid' => 1, ' country' => 'China','province'=>'Beijing'),
 array('id'=>6,'cid' => 1, 'country' => 'China',' province'=>'Shandong'),
 array('id'=>7,'cid' => 1, 'country' => 'China','province'=>'Shandong'),
 array('id'=>8,'cid' => 2, 'country' => 'United States','province'=>'Ontario'),
 array('id'=>9 ,'cid' => 2, 'country' => 'United States','province'=>'Ontario'),
 array('id'=>10,'cid' => 3, ' country' => 'Japan','province'=>'Nagoya'),
);
//Reference answer:
/*
 Basically all operations on data are correct The data in the array is restructured. If you learn how to construct the structure of the array, you will also master how to use the data. The home page of this question needs to construct the array structure to be output at the end. This array structure can be final or indirect. The following is a way of constructing an array:
$ary =array(
 'China'=>array('Hunan'=>2,'Shandong'=>2,'Beijing'=>1),
 'Japan'=>array('Nagoya'=>2,'Tokyo'=>1),
 'United States'=>array(),
);
*/
< p>$data = array();
foreach($arr as $k=>$v){
 @$data[$v['country']][$v['province']] +=1; //Determine the key points of this question and experience it more.
}
//The final structure of the data
echo 'Country:',count($data),'';
foreach($data as $k=>$v){
 echo '     ',$k,':',array_sum($v),'times';
 echo '        Province:',count( $v),'a';
 foreach($v as $kk=>$vv){
 echo '       ',$kk,' :',$vv,'times';
 }
}
?>

Output results: Countries: 3 China: 5 times Provinces: 3 Hunan: 2 times Beijing: 1 time Shandong: 2 times Japan: 3 times Provinces: 2 Nagoya: 2 times Tokyo: 1 time United States: 2 times Province: 1 Ontario: 2 times Friends who are interested should have a good understanding of the application skills of arrays in the above code and understand this sentence:

 foreach($arr as $k=>$v){
 @$data[$v['country']][$v['province']] +=1; //Definitely Please understand the key points of the question.
}

Master the practical skills of php arrays.