【array_count_values】计算数组中每个值出现的个数,数组中只能包含数字或者字符串
array_count_values( array $array) : array
<?php
$array = array(1, "hello", 1, "world", "hello");
$result = array_count_values($array);
var_dump($result);
/*
array(3) {
[1]=>
int(2)
["hello"]=>
int(2)
["world"]=>
int(1)
}
*/
# 计算某个键值对出现的次数
$list = [
['id' => 1, 'userId' => 5],
['id' => 2, 'userId' => 5],
['id' => 3, 'userId' => 6],
];
echo array_count_values(array_column($list, 'userId'))[5];
/*
2
*/