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[(Key) Four ways of circulating through arrays]
1.
## conut($arr); used to count the number of array elements.
The for loop can only be used to traverse, pure index arrays! ! ! !
If there is an associative array, the total number of the two arrays will be counted during count statistics, and a for loop will be used to traverse the mixed array, causing the array to go out of bounds! !
eg:
$arr = array(1,2,3,5,6,7);
$num = Count ($ Arr); // Count is best placed outside the outside, which can allow the function to execute only ## Echo. br/>";
for($i=0;$i<$num;$i++){
echo "{$i}==> ;{$arr[$i]}
";
}
2. forEach loops through the array foreach can traverse any type of array! ! !
eg:
$arr = array(1,2,3,"one"=>4,5,6,7); foreach($arr as $value){ echo "{$item}
"; } foreach($arr as $key => $value){ echo "{$key}==>{$item}
"; }
##An example is as follows Array: $h51701 ==>=>,=>,=>=>,=>,=>=>,=>,=>=>=>,=>,=>=>,=>,=>=>,=>,=>=>=>,=>,=>=>,=>,=>=>,=>,=> ($h51701 $key => ($value $key1 =>.($key1+). ($value1 $key2 =>
使用list()、each()、while()遍历数组
(重点)list():用于将数组的每一个值,赋值给list函数的每一个参数。(list函数的参数,必须小于等于数组的元素个数);
eg:list($a,$b,$c)=[1,2,3];-->$a=1; $b=2; $c=3;
注意:① list()在解析数组时,只解析索引数组;
② list可以通过空参数,选择性的解析数组的值;
list($a,,$b)=[1,2,3];-->$a=1; $b=3;
(重点)each():用于返回数组当前指针所在位的键值对!并将指针后移一位;
返回值:如果指针有下一位,返回一个数组。包含一个索引数组(0-键,1-值)和一个关联数组("key"-键,"value"-值);如果指针没有下一位,返回false;
eg:
① each($arr) 返回数组或false;
② 把数组或false赋值给$a;
③ while判断$a如果是数组,继续执行下一次;
如果$a是false,终止循环
while($a = each($arr)){
echo "{$a[0]}-->{$a[1]}
";
echo "{$a['key']}-->{$a['value']}
";
}
3.使用list()/each()/while()配合遍历数组
while(list($key,$value) = each($arr)){ echo "{$key}-->{$value}
"; } reset($arr);
!!!!数组使用each()遍历完一遍后,指针使用处于最后一位的下一位;即再用each(),始终返回false;
如果还需使用,需用reset($arr);函数,重置数组指针;
eg:
$arr = array(1,2,3,"one"=>4,5,6,7); foreach($arr as $value){ echo "{$item}
"; } foreach($arr as $key => $value){ echo "{$key}==>{$item}
"; }
(=
while(list($key,$value) = each($arr)){ echo "{$key}-->{$value}
"; } reset($arr); while(list($key,$value) = each($arr)){ echo "{$key}-->{$value}
"; }
4、 使用数组指针遍历数组
① next:将数组指针,后移一位。并返回后一位的值;没有返回false
② prev:将数组指针,前移一位。并返回前一位的值;没有返回false
③ end: 将数组指针,移至最后一位,返回最后一位的值;空数组返回false
④ reset:将数组指针,恢复到第一位。并返回第一位的值;空数组返回false
⑤ key: 返回当前指针所在位的键;
⑥ current:返回当前指针所在位的值;
$arr = [,,,,=>((!
do{ echo key($arr); echo "--"; echo current($arr); echo "
"; }while(next($arr)); reset($arr);
牛刀小试:
1.遍历数组:$subject1 = array("Linux","PHP","MySQL","HTML","CSS","JQuery")
方式一:for循环遍历
for($i=0;$i"; }
方式二:使用list()/each()/while()配合遍历数组
. (list($key,$value)=
方式三:forEach循环遍历
foreach ($subject1 as $key => $value) { echo "{$key}-->{$value}
"; }
方式四:指针
do{
echo key($subject1)."=>".current($subject1)."
";
}while(next($subject1));
echo "
";
2.使用reset(),end(),prev(),next(),key(),current();与do…while组合倒着输出数组中的值:
$subject2 = array(“Linux”,”PHP”,”MySQL”,”HTML”,”CSS”,”JQuery”)
$subject2 = array("Linux","PHP","MySQL","HTML","CSS","JQuery"); end($subject2); do{ echo key($subject2)."=>".current($subject2)."
"; }while(prev($subject2));
感觉不错就试试吧!!!
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