1.函数的作用：返回数组当前元素位置的下一个元素
2.函数的参数：
@param array &$array
3.
例子一：数组拷贝时，内部指针的位置也一起拷贝
1 <?php 2 $arr1 = ['last','next']; 3 next($arr1); 4 $arr2 = $arr1; 5 echo "Pointer of arr1 is " .key($arr1) .". The value is '" . current($arr1) ."' "; 6 echo "Pointer of arr2 is " .key($arr2) .". The value is '" . current($arr1) ."' ";
例子二： foreach 之后数组内部指针的位置不重置
1 <?php 2 $arr1 = ['last','next']; 3 foreach($arr1 as $key => $value){ 4 echo "Number $key's value : $value "; 5 } 6 $str = is_null(key($arr1)); 7 echo "The current key of the array of arr1 is " . ($str ? 'null' : $str) ;
例子三：
1 <?php 2 $arr1 = ['last','next']; 3 next($arr1); 4 $arr2 = array_values($arr1); 5 6 echo "The pointer's position of the array of arr1 is " .key($arr1) . " "; 7 echo "The pointer's position of the array of arr1 is " .key($arr2) . " ";
例子四：接下来是比较奇异的两个地方，传数组参数给函数，看看指针的位置的情况：
1）指针重置的情况：
1 <?php 2 function testPointerPosition($array){ 3 echo "The current element of array in function is '" .current($array)."' and current key is " .key($array)." "; 4 } 5 6 $arr1 = ['last','next']; 7 next($arr1); 8 next($arr1); 9 testPointerPosition($arr1);
2）指针未重置的情况：
1 <?php 2 function testPointerPosition($array){ 3 echo "The current element of array in function is '" .current($array)."' and current key is " .key($array)." "; 4 } 5 6 $arr1 = ['last','next']; 7 next($arr1); 8 testPointerPosition($arr1);
例子五：有的时候使用next()函数之后，你想判断该元素是不是存在，结果你这么用：
1 <?php 2 $arr = [1,false]; 3 next($arr); 4 if(current($arr)){ 5 echo "The element exist! "; 6 }else{ 7 echo "The element doesn't exist! "; 8 }
刚好有个 false 元素，就有了错误的输出。所以应该这么用：
1 <?php 2 $arr = [1,false]; 3 next($arr); 4 if(key($arr) === false){ 5 echo "Current element doesn't exist! "; 6 }else{ 7 echo "Current element exist! "; 8 }
记住用 “===” 符号。数组不会有键值为false的类型的，即使你初始化的时候，用false作键值，内部也会将其解释为 0，并覆盖先前的键值为 0 的元素。