array

//创建数组
$arr = array("one", "two");

in_array

//判断变量是否在数组中
$people = array("Bill", "Steve", "Mark", "David");
echo in_array("Bill", $people); //true

count

//对于数组，返回其元素的个数，对于其他值，返回 1。如果参数是变量而变量没有定义，则返回 0
$people = array("Bill", "Steve", "Mark", "David");
count($people); //4
count('3213refds'); //1
count($a); //0

array_count_values

//统计数组中的值出现的次数
$a=array("A","Cat","Dog","A","Dog");
print_r(array_count_values($a));//Array ( [A] => 2 [Cat] => 1 [Dog] => 2 )

array_column

//返回输入数组中某个单一列的值
$a = array(
  array(
    'first_name' => 'Peter',
    'last_name' => 'Griffin',
  ),
  array(
    'first_name' => 'Ben',
    'last_name' => 'Smith',
  )
);

$last_names = array_column($a, 'last_name');
print_r($last_names); //Array( [0] => Griffin  [1] => Smith )

array_diff

//比较两个数组的值，并返回差集
$a1=array("a"=>"red","b"=>"green","c"=>"blue","d"=>"yellow");
$a2=array("e"=>"red","f"=>"green","g"=>"blue");
 
$result=array_diff($a1,$a2);
print_r($result); //Array ( [d] => yellow )

array_intersect

//返回两个数组的交集

array_keys

//返回数组中所有的键名