php 获取数组第一个值的方法分享

reset (PHP 3, PHP 4, PHP 5)
reset -- 将数组的内部指针指向第一个单元

说明
mixed reset ( array &array )
reset() 将 array 的内部指针倒回到第一个单元并返回第一个数组单元的值，如果数组为空则返回 FALSE。

例 1. reset() 例子

<?<span php
</span><span //</span><span 获取数组第一个值
//by www.jbxue.com</span>
<span $array</span> = <span array</span>('stepone', 'step two', 'step three', 'step four'<span );
</span><span //</span><span by default, the pointer is on the first element</span>
<span echo</span> <span current</span>(<span $array</span>) . "<br/>\n"; <span //</span><span  "stepone"
// skip twosteps</span>
<span next</span>(<span $array</span><span );
</span><span next</span>(<span $array</span><span );
</span><span echo</span> <span current</span>(<span $array</span>) . "<br/>\n"; <span //</span><span  "stepthree"
//reset pointer, start again on step one</span>
<span reset</span>(<span $array</span><span );
</span><span echo</span> <span current</span>(<span $array</span>) . "<br/>\n"; <span //</span><span  "stepone"</span>
?>

next -- 将数组中的内部指针向前移动一位

说明
mixed next ( array &array )
返回数组内部指针指向的下一个单元的值，或当没有更多单元时返回 FALSE。

next() 和 current()的行为类似，只有一点区别，在返回值之前将内部指针向前移动一位。这意味着它返回的是下一个数组单元的值并将数组指针向前移动了一位。如果移动指针的结果是超出了数组单元的末端，则next() 返回 FALSE。

警告
如果数组包含空的单元，或者单元的值是 0 则本函数碰到这些单元也返回 FALSE。要正确遍历可能含有空单元或者单元值为 0的数组，参见 each() 函数。

例 1. next() 及相关函数的用法示例

<?<span php
</span><span //</span><span 数组迭代方法 next
//by www.jbxue.com</span>
<span $transport</span> = <span array</span>('foot', 'bike', 'car', 'plane'<span );
</span><span $mode</span> = <span current</span>(<span $transport</span>); <span //</span><span $mode = 'foot';</span>
<span $mode</span> = <span next</span>(<span $transport</span>); <span //</span><span  $mode ='bike';</span>
<span $mode</span> = <span next</span>(<span $transport</span>); <span //</span><span  $mode ='car';</span>
<span $mode</span> = <span prev</span>(<span $transport</span>); <span //</span><span  $mode ='bike';</span>
<span $mode</span> = <span end</span>(<span $transport</span>); <span //</span><span  $mode ='plane';</span>
?>

current -- 返回数组中的当前单元

说明
mixed current ( array &array )

每个数组中都有一个内部的指针指向它“当前的”单元，初始指向插入到数组中的第一个单元。
current() 函数返回当前被内部指针指向的数组单元的值，并不移动指针。如果内部指针指向超出了单元列表的末端，current()返回 FALSE。

警告
如果数组包含有空的单元（0 或者 ""，空字符串）则本函数在碰到这个单元时也返回 FALSE。这使得用 current()不可能判断是否到了此数组列表的末端。要正确遍历可能含有空单元的数组，用 each() 函数。

例 1. current() 及相关函数的用法示例

<?<span php
</span><span //</span><span 取当前数组元素</span>
<span $transport</span> = <span array</span>('foot', 'bike', 'car', 'plane'<span );
</span><span $mode</span> = <span current</span>(<span $transport</span>); <span //</span><span $mode = 'foot';</span>
<span $mode</span> = <span next</span>(<span $transport</span>); <span //</span><span  $mode ='bike';</span>
<span $mode</span> = <span current</span>(<span $transport</span>); <span //</span><span $mode = 'bike';</span>
<span $mode</span> = <span prev</span>(<span $transport</span>); <span //</span><span  $mode ='foot';</span>
<span $mode</span> = <span end</span>(<span $transport</span>); <span //</span><span  $mode ='plane';</span>
<span $mode</span> = <span current</span>(<span $transport</span>); <span //</span><span $mode = 'plane';
//by www.jbxue.com 脚本学堂</span>
?>