php array相关函数个人小结
1.array_chunk() 把一个数组分割为新的数组块。其中每个数组的单元数目由 size 参数决定。最后一个数组的单元数目可能会少几个。
例子
$a=array("a"=>"Cat","b"=>"Dog","c"=>"Horse","d"=>"Cow");
print_r(array_chunk($a,2));
?>
输出：
Array (
[0] => Array ( [0] => Cat [1] => Dog )
[1] => Array ( [0] => Horse [1] => Cow )
)
【
这里非常像linux里的split工具。
[root@xen187v tmp]$ cat tmp
1
2
3
4
5
6
7
[root@xen187v tmp]$ split -l 2 tmp
[root@xen187v tmp]$ ls
tmp xaa xab xac xad
[root@xen187v tmp]$ cat xaa
1
2
[root@xen187v tmp]$ cat xab
3
4
[root@xen187v tmp]$ cat xac
5
6
[root@xen187v tmp]$ cat xad
7
】
2.
array_merge() 把一个或多个数组合并为一个数组。【这个是纵向合并】
array_combine() 函数通过合并两个数组来创建一个新数组，其中的一个数组是键名，另一个数组的值为键值。【这个是横向合并】
如果其中一个数组为空，或者两个数组的元素个数不同，则该函数返回 false。
例子
$a1=array("a","b","c","d");
$a2=array("Cat","Dog","Horse","Cow");
print_r(array_combine($a1,$a2));
?>
【
这个很像linux下的paste命令类似。
paste单词意思是粘贴。该命令主要用来将多个文件的内容合并，与cut命令完成的功能刚好相反。
粘贴两个不同来源的数据时，首先需将其分类，并确保两个文件行数相同
[root@xen187v tmp]$ cat xaa
1
2
[root@xen187v tmp]$ cat xab
3
4
[root@xen187v tmp]$ paste xaa xab
1 3
2 4
给xaa多加一行看看会怎么样
[root@xen187v tmp]$ cat xaa
1
2
3
[root@xen187v tmp]$ paste xaa xab
1 3
2 4
3
给xab再加两行看看怎样样
[root@xen187v tmp]$ cat xab
i
i
3
4
[root@xen187v tmp]$ paste xaa xab
1 i
2 i
3 3
4
[root@xen187v tmp]$
】
3.
array_sum() 计算数组中所有值的和。
array_count_values() 函数用于统计数组中所有值出现的次数。
本函数返回一个数组，其元素的键名是原数组的值，键值是该值在原数组中出现的次数。
【很像uniq -c
[root@xen187v tmp]$ cat xab
i
i
3
4
[root@xen187v tmp]$ uniq -c xab
2 i
1 3
1 4
[root@xen187v tmp]$ uniq -c xab|awk '{print $2" "$1}'
i 2
3 1
4 1
[root@xen187v tmp]$
】
4.
【感慨：要是这些数组函数名和linux命令名一致该多好，方便记忆】
5.array_diff() 函数返回第一个数组，不在后继数组中的数据项数组
6.array_flip()交换数组中的键和值. 函数返回一个反转后的数组，如果同一值出现了多次，则最后一个键名将作为它的值，所有其他的键名都将丢失。
如果原数组中的值的数据类型不是字符串或整数，函数将报错。
【这个值得记忆，处理数据时，容易遇到key->value要翻转的情况】
7.array_intersect() 计算数组的交集。
【
面试中容易出的题，用原生代码求两个数组的交集
function intersectArray($arr1,$arr2)
{
$tmpArr = array();
foreach($arr1 as $v1) $tmpArr[$v1] = 0;
foreach($arr2 as $v2)
{
if(isset($tmpArr[$v2])
{
$tmpArr[$v2] = 1;
}
}
//$tmpArr中值为1的就是交集
$retArr = array();
foreach($tmpArr as $key => $v)
{
if($v == 1) $retArr[] = $key;
}
return $retArr;
}
】
8.array_keys() 返回数组中所有的键名。
9.
array_rand() 从数组中随机选出一个或多个元素，并返回。
shuffle() 函数把数组中的元素按随机顺序重新排列
10.
array_reverse() 将原数组中的元素顺序翻转，创建新的数组并返回。
11.
array_search() 在数组中搜索给定的值，如果成功则返回相应的键名。
12
array_unique() 删除数组中重复的值。
13
arsort() 对数组进行逆向排序并保持索引关系。
asort() 对数组进行排序并保持索引关系。
krsort() 对数组按照键名逆向排序。
ksort() 对数组按照键名排序。
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