PHP prev() 函数
实例
输出数组中的当前元素、下一个元素和上一个元素的值:
<?php
$people = array("Peter", "Joe", "Glenn", "Cleveland");
echo current($people) . "<br>";
echo next($people) . "<br>";
echo prev($people);
?>
亲自试一试 »
$people = array("Peter", "Joe", "Glenn", "Cleveland");
echo current($people) . "<br>";
echo next($people) . "<br>";
echo prev($people);
?>
定义和用法
prev() 函数将内部指针指向数组中的上一个元素,并输出。
相关的方法:
- next() - 将内部指针指向数组中的下一个元素,并输出
- current() - 返回数组中的当前元素的值
- end() - 将内部指针指向数组中的最后一个元素,并输出
- reset() - 将内部指针指向数组中的第一个元素,并输出
- each() - 返回当前元素的键名和键值,并将内部指针向前移动
语法
prev(array)
参数值
参数 | 描述 |
---|---|
array | 必需。指定要使用的数组 |
说明
prev() 和 next() 的行为类似,不过它将内部指针倒回一位而不是前移一位。
注意:如果数组包含空的单元,或者单元的值是 0 则该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,请参见 each() 函数。
技术细节
返回值: | 如果成功则返回数组中上一个元素的值,如果没有更多的数组元素则返回 FALSE。 |
---|---|
PHP 版本: | 4+ |
更多实例
实例
演示所有相关的方法:
<?php
$people = array("Peter", "Joe", "Glenn", "Cleveland");
echo current($people) . "<br>"; // The current element is Peter
echo next($people) . "<br>"; // The next element of Peter is Joe
echo current($people) . "<br>"; // Now the current element is Joe
echo prev($people) . "<br>"; // The previous element of Joe is Peter
echo end($people) . "<br>"; // The last element is Cleveland
echo prev($people) . "<br>"; // The previous element of Cleveland is Glenn
echo current($people) . "<br>"; // Now the current element is Glenn
echo reset($people) . "<br>"; // Moves the internal pointer to the first element of the array, which is Peter
echo next($people) . "<br>"; // The next element of Peter is Joe
print_r (each($people)); // Returns the key and value of the current element (now Joe), and moves the internal pointer forward
?>
亲自试一试 »
$people = array("Peter", "Joe", "Glenn", "Cleveland");
echo current($people) . "<br>"; // The current element is Peter
echo next($people) . "<br>"; // The next element of Peter is Joe
echo current($people) . "<br>"; // Now the current element is Joe
echo prev($people) . "<br>"; // The previous element of Joe is Peter
echo end($people) . "<br>"; // The last element is Cleveland
echo prev($people) . "<br>"; // The previous element of Cleveland is Glenn
echo current($people) . "<br>"; // Now the current element is Glenn
echo reset($people) . "<br>"; // Moves the internal pointer to the first element of the array, which is Peter
echo next($people) . "<br>"; // The next element of Peter is Joe
print_r (each($people)); // Returns the key and value of the current element (now Joe), and moves the internal pointer forward
?>