一、合并、拆分、接合和分解数组

1、合并数组

array_merge() 函数将数组合并在一起，返回一个新数组。

$a = array("a","b","c");$b = array("d","e","f");$c = array_merge($b,$a);print_r($c); //Array ( [0] => d [1] => e [2] => f [3] => a [4] => b [5] => c )

2、递归追加数组

array_merge_recursive() 函数与 array_merge() 函数都是合并数组，两者的区别在于当输入数组用有某个键已经存在的时候的处理方法的不同：

array_merge：覆盖前面的同名键值；

array_merge_recursive：合并同名键为一个以键值为数组名称的数组，数组值为同名键的值的集合。

$a = array("k1"=>"a","k2"=>"b","k3"=>"c");$b = array("k1"=>"d","k4"=>"e","k5"=>"f");$c = array_merge($b,$a);print_r($c); //Array ( [k1] => a [k4] => e [k5] => f [k2] => b [k3] => c )

print "
";$d = array_merge_recursive($b,$a); //Array ( [k1] => Array ( [0] => d [1] => a ) [k4] => e [k5] => f [k2] => b [k3] => c )

print_r($d);

3、合并数组

array_combine() 数组与array_merge()不同之处再约array_merge是合并数组的值，array_combine是用第一个数组的值作为第二个数组的键，所以array_combine的输入参数的大小必须相同。

$a = array("k1"=>"a","k2"=>"b","k3"=>"c");$b = array("k1"=>"d","k4"=>"e","k5"=>"f");$c = array_combine($b,$a);print_r($c); //Array ( [d] => a [e] => b [f] => c )

4、拆分数组

array_slice() 函数将返回数组中的一部分，从offset键开始，到offset + length位置结束。

$a = array("k1"=>"a","k2"=>"b","k3"=>"c","k4"=>"d","k5"=>"e","k6"=>"f");$c = array_slice($a,3);print_r($c); //Array ( [k4] => d [k5] => e [k6] => f )

5、截取数组

array_splice() 函数将会截取数组中从offse开始，到offset + length位置结束的所有元素，并返回截取的元素(以数组形式)。

截取后，原数组则剩余未被截取部分。

$a = array("k1"=>"a","k2"=>"b","k3"=>"c","k4"=>"d","k5"=>"e","k6"=>"f");$c = array_splice($a,3);print_r($c); //Array ( [k4] => d [k5] => e [k6] => f )

print "
";print_r($a); //Array ( [k1] => a [k2] => b [k3] => c )

可选参数replacement可以用一个数组填充被截取的部分到原数组中。

$a = array("k1"=>"a","k2"=>"b","k3"=>"c","k4"=>"d","k5"=>"e","k6"=>"f");$c = array_splice($a,3,3,array("k7"=>"g","k8"=>"h"));print_r($c); //Array ( [k4] => d [k5] => e [k6] => f )

print "
";print_r($a); //Array ( [k1] => a [k2] => b [k3] => c [0] => g [1] => h )

6、求数组的交集

array_intersect() 函数 返回输入数组的值的交集。

扩展：array_intersect_key() 获取数组的键的交集。array_intersect_ukey() 允许用户自定义函数进行键比较。

$a = array("A","B","C","D");$b = array("E","F","G","H","B","C");$c = array("I","J","B","K","C","L");$d = array_intersect($a,$b,$c);print_r($d); //Array ( [1] => B [2] => C )

7、求关联数组的交集

array_intersect_assoc() 函数除了和 array_intersect() 一样比较值之外，还比较键是否相同。就是说，它取键值对一致的交集。

$a = array("a"=>"A","b"=>"B","C","D");$b = array("E","F","G","H","b"=>"B","C");$c = array("I","J","b"=>"B","K","C","L");$d = array_intersect_assoc($a,$b,$c);print_r($d); //Array ( [b] => B )

8、求数组的差集

array_diff() 函数求数组的差集，和 array_intersect() 相反。(是指获取第一个数组中有，但是其他数组中没有的值！)

$a = array("a"=>"A","b"=>"B","C","D");$b = array("E","F","G","H","b"=>"B","C");$c = array("I","J","b"=>"B","K","C","L");$d = array_diff($a,$b,$c);print_r($d); //Array ( [a] => A [1] => D )

9、求关联数组的差集

array_diff_assoc() 函数和 array_diff() 基本一致，不过它对键值对进行比较。

扩展：array_udiff_assoc()、array_udiff_uassoc()、array_diff_uassoc()等函数加入自定义函数进行比较。

$a = array("a"=>"A","b"=>"B","C","D");$b = array("E","F","G","H","b"=>"B","C");$c = array("I","J","b"=>"B","K","C","L");$d = array_diff_assoc($a,$b,$c);print_r($d); //Array ( [a] => A [0] => C [1] => D )

二、其他有用的数组函数

1、返回一组随机的键

array_rand() 函数将返回数组中一个或多个随机的键！

$a = array("a"=>"A","b"=>"B","c"=>"C","d"=>"D");$d = array_rand($a,2);print_r($d); //Array ( [0] => a [1] => d ) 随机结果

2、随机打乱数组元素

shuffle() 函数随机地对数组元素进行重新排序。关联数组中的键会丢失。

$a = array("a"=>"A","b"=>"B","c"=>"C","d"=>"D");shuffle($a);print_r($a); //Array ( [0] => C [1] => A [2] => B [3] => D ) 随机结果

3、对数组中的值求和

array_sum() 函数将对数组中的值加在一起求和并返回和。

$a = array(1,2,3,4,5,6,7,8);$sum = array_sum($a);echo $sum; //36

4、划分数组

array_chunk() 函数将数组划分为size大小的多维数组。

$a = array(1,2,3,4,5,6,7,8);$s = array_chunk($a,3);print_r($s); //Array ( [0] => Array ( [0] => 1 [1] => 2 [2] => 3 ) [1] => Array ( [0] => 4 [1] => 5 [2] => 6 ) [2] => Array ( [0] => 7 [1] => 8 ) )