php 如何测试数组指针是否在foreach循环中的第一个元素
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how to test if array pointer is at first element in foreach loop
提问by AlexMorley-Finch
In a for loop it is simple...
在 for 循环中很简单......
for ( $idx = 0 ; $idx < count ( $array ) ; $idx ++ )
{
if ( $idx == 0 )
{
// This is the first element of the array.
}
}
How the hell is this done in a foreach loop?
这到底是如何在 foreach 循环中完成的？
is there a function like is_first()or something?
有类似的功能is_first()吗？
I'm looking for something like:
我正在寻找类似的东西：
foreach ( $array as $key => $value )
{
if ( /* is the first element */ )
{
// do logic on first element
}
else
{
// all other logic
}
}
I was thinking I could set a bool like $is_first = true;and then as soon as the loops been iterated once, set the bool to false.
我在想我可以设置一个 bool $is_first = true;，然后一旦循环迭代一次，就将 bool 设置为 false。
But php has a lot of pre-built functions and id rather use that... or another way...
但是 php 有很多预先构建的函数，而 id 宁愿使用它......或其他方式......
The whole bool way seem almost like... cheeting :s
整个布尔方式看起来几乎就像...... cheeting :s
Cheers,
干杯，
Alex
亚历克斯
回答by Choy
I usually do this :
我通常这样做：
$isFirst = true;
foreach($array as $key => $value){
if($isFirst){
//Do first stuff
}else{
//Do other stuff
}
$isFirst = false;
}
Works with any type of array, obviously.
显然，适用于任何类型的数组。
回答by RobinUS2
You can do this using "current()"
您可以使用“current()”来做到这一点
$myArray = array('a', 'b', 'c');
if (current($myArray) == $myArray[0]) {
// We are at the first element
}
Docs: http://php.net/manual/en/function.current.php
文档：http: //php.net/manual/en/function.current.php
Ways of retrieving the first element:
检索第一个元素的方法：
$myArray[0]
$slice = array_slice($myArray, 0, 1);
$elm = array_pop($slice);
回答by Mark Baker
$myArray = array('a' => 'first', 'b' => 'second', 'c' => 'third');
reset($myArray);
$firstKey = key($myArray);
foreach($myArray as $key => $value) {
if ($key === $firstKey) {
echo "I'm Spartacus" , PHP_EOL;
}
echo $key , " => " , $value , PHP_EOL;
}
回答by Haim Evgi
you can use counter instead bool
你可以使用 counter 代替 bool
$i = 0;
foreach ( $array as $key => $value )
if ($i == 0) {
// first
} else {
// last
}
// …
$i++;
}
or extract the first element by
或通过以下方式提取第一个元素
$first = array_shift($array);
and foreachover the remain array;
并foreach在剩余数组上；
回答by Gaurav
$first = array_shift($idx);
foreach($idx as $key => $value){
...
...
...
}
回答by m0skit0
You can just put the operation on first element before the foreachloop, remove the element and then enter the foreachloop for the rest of the elements.
您可以将操作放在foreach循环之前的第一个元素上，删除该元素，然后为其余元素进入foreach循环。
回答by Dieter Gribnitz
Here are two functions that will detect if an array key is first or last.
这里有两个函数可以检测数组键是第一个还是最后一个。
If no key is provided it will assume the current pointer position.
如果没有提供键，它将采用当前的指针位置。
In a foreach loop you will need to provide the key since the pointer will not be correct.
在 foreach 循环中，您需要提供密钥，因为指针将不正确。
public static function isFirst($array, $key=null)
{
if($key===null){
$key = key($array);
}
reset($array);
$first = key($array);
return $first === $key;
}
public static function isLast($array, $key=null)
{
if($key===null){
$key = key($array);
}
end($array);
$last = key($array);
return $last === $key;
}
