php array数组（第一部分）

创建一个数组

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<?php
    $arr = array("My","name","is","zhangsan");
    echo $arr[0]." ".$arr[1]." ".$arr[2]." ".$arr[3];
?>

//输出
My name is zhangsan

array_change_key_case() 将数组的所有键值转换为大写

参数 CASE_UPPER 转换为大写
参数 CASE_LOWER 转换为小写

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<?php
   $age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");
   print_r(array_change_key_case($age,CASE_UPPER));
?>

//输出
Array ( [PETER] => 35 [BEN] => 37 [JOE] => 43 )

array_chunk() 把一个数组分割为新的数组块

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<?php
    $cars=array("Volvo","BMW","Toyota","Honda","Mercedes","Opel");
    print_r(array_chunk($cars,2));
?>

//输出
Array
(
    [0] => Array
        (
            [0] => Volvo
            [1] => BMW
        )

    [1] => Array
        (
            [0] => Toyota
            [1] => Honda
        )

    [2] => Array
        (
            [0] => Mercedes
            [1] => Opel
        )

)

array_column() 返回输入数组中某个单一列的值

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<?php
// 可能从数据库中返回数组
$a = array(
  array(
    'id' => 5698,
    'first_name' => 'Peter',
    'last_name' => 'Griffin',
  ),
  array(
    'id' => 4767,
    'first_name' => 'Ben',
    'last_name' => 'Smith',
  ),
  array(
    'id' => 3809,
    'first_name' => 'Joe',
    'last_name' => 'Doe',
  )
);

$last_names = array_column($a, 'last_name');
print_r($last_names);
?>

//输出
Array
(
  [0] => Griffin
  [1] => Smith
  [2] => Doe
)

array_combine() 通过合并两个数组来创建一个新数组，其中的一个数组元素为键名，另一个数组的元素为键值。

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<?php
    $fname=array("Peter","Ben","Joe");
    $age=array("35","37","43");
    $c=array_combine($fname,$age);
    print_r($c);
?>

//输出
Array ( [Peter] => 35 [Ben] => 37 [Joe] => 43 )

array_count_values() 统计数组中所有值出现的次数

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<?php
    $a=array("A","Cat","Dog","A","Dog");
    print_r(array_count_values($a));
?>

//输出
Array ( [A] => 2 [Cat] => 1 [Dog] => 2 )

array_diff() 用于比较两个(或更多个)数组的键值,并返回差集（只比较键值）

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<?php
    $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);
?>

//输出
Array ( [d] => yellow )

array_diff_assoc() 用于比较两个(或更多个)数组的键名和键值,并返回差集。

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<?php
    $a1=array("a"=>"red","b"=>"green","c"=>"blue","d"=>"yellow");
    $a2=array("a"=>"red","b"=>"green","c"=>"blue");
    
    $result=array_diff_assoc($a1,$a2);
    print_r($result);
?>

//输出
Array ( [d] => yellow )


<?php
    $a1=array("a"=>"red","b"=>"green","c"=>"blue","d"=>"yellow");
    $a2=array("e"=>"red","f"=>"green","g"=>"blue");
    
    $result=array_diff_assoc($a1,$a2);
    print_r($result);
?>

//输出
Array ( [a] => red [b] => green [c] => blue [d] => yellow )

array_diff_key() 用于比较两个(或更多个)数组的键名，并返回差集

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<?php
    $a1=array("a"=>"red","b"=>"green","c"=>"blue");
    $a2=array("a"=>"red","c"=>"blue","d"=>"pink");
    
    $result=array_diff_key($a1,$a2);
    print_r($result);
?>
//输出
Array ( [b] => green )

array_diff_uassoc() 用于比较两个(或更多个)数组的键名和键值，并返回差集(该函数使用用户自定义函数比较键名和键值)。

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<?php
function myfunction($a,$b)
{
    if ($a===$b)
    {
       return 0;
    }
    return ($a>$b)?1:-1;
}

$a1=array("a"=>"red","b"=>"green","c"=>"blue");
$a2=array("d"=>"red","b"=>"green","e"=>"blue");

$result=array_diff_uassoc($a1,$a2,"myfunction");
print_r($result);
?>

//输出
Array ( [a] => red [c] => blue )

array_diff_ukey() 用于比较两个(或更多)数组的键名，并返回差集(该函数使用用户自定义函数比较键名)

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<?php
function myfunction($a,$b)
{
   if ($a===$b)
   {
      return 0;
   }
   return ($a>$b)?1:-1;
}

$a1=array("a"=>"red","b"=>"green","c"=>"blue");
$a2=array("a"=>"blue","b"=>"black","e"=>"blue");

$result=array_diff_ukey($a1,$a2,"myfunction");
print_r($result);
?>

//输出
Array ( [c] => blue )