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PHP遍历数组的几种方法_php技巧

May 17, 2016 am 09:11 AM
Traverse array

PHP中遍历数组有三种常用的方法:
一、使用for语句循环遍历数组;
二、使用foreach语句遍历数组;
三、联合使用list()、each()和while循环遍历数组。
这三种方法中效率最高的是使用foreach语句遍历数组。从PHP4开始就引入了foreach结构,是PHP中专门为遍历数组而设计的语句,推荐大家使用。先分别介绍这几种方法。

一、使用for语句循环遍历数组
值得大家注意的是使用for语句循环遍历数组要求遍历的数组必须是索引数组。PHP中不仅有关联数组而且还有索引数组,所以PHP中很少用for语句循环遍历数组。
实例代码如下:

复制代码 代码如下:

$arr = array('http://www.jb51.net','脚本之家','PHP教程');
$num = count($arr);
for($i=0;$iecho $arr[$i].'
';
}
?>

注释:上例代码中我们先计算出数组$arr中元素的个数,然后才使用在for语句,这样做很高效的。因为如果是for($i=0;$i上面代码的输出结果为:
http://www.jb51.net
脚本之家
PHP教程

二、使用foreach语句遍历数组
使用foreach语句循环遍历数组有二种方式,我们使用的最多的还是第一种方式。介绍如下:
第一种方式:
foreach(array_expression as $value){
//循环体
}
实例代码:
复制代码 代码如下:

$arr = array('http://www.jb51.net','脚本之家','PHP教程');
foreach($arr as $value){
echo $value.'
';
}
?>


每次循环中,当前元素的值被赋给变量$value,并且把数组内部的指针向后移动一步。所以下一次循环中会得到数组的下一个元素,直到数组的结尾才停止循环,结束数组的遍历。

第二种方式:
foreach(array_expression as $key=>$value){
//循环体
}
实例代码:
复制代码 代码如下:

//定义数组
$arr = array('http://www.jb51.net','脚本之家','PHP教程');
foreach($arr as $k=>$v){
echo $k."=>".$v."
";
}
?>


三、联合使用list()、each()和while循环遍历数组
each()函数需要传递一个数组作为一个参数,返回数组中当前元素的键/值对,并向后移动数组指针到下一个元素的位置。
list()函数,这不是一个真正的函数,是PHP的一个语言结构。list()用一步操作给一组变量进行赋值。

实例代码:
复制代码 代码如下:

//定义循环的数组
$arr = array('website'=>'http://www.jb51.net','webname'=>'脚本之家')
while(list($k,$v) = each($arr)){
echo $k.'=>'.$v.'
';
}
?> jb51.net

输出结果为:
website=>http://www.jb51.net
webname=>PHP程序员

总结:上述三种循环遍历数组的方法中建议大家使用foreach语句循环遍历数组,效率更高。
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