如何打印或回显 PHP 中的数组索引
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How to print or echo the array index of in PHP
提问by Ali
I'm trying to complete my assignment and this is the last thing to do now.
我正在努力完成我的任务，这是现在要做的最后一件事。
I know if I want to print the whole array I can just use foreachand many different method to print the entire array
我知道如果我想打印整个数组，我可以使用foreach许多不同的方法来打印整个数组
foreach($v as $k=>$variable_name) { echo "<p> This is index of $k. value is $variable_name <br/></p>";}
But what if I want to only print each index separately?
但是如果我只想单独打印每个索引怎么办？
I want to do the error message under each form so that is why I want each of them separate.
我想在每个表单下显示错误消息，这就是为什么我希望每个表单都分开。
I tried with $v[0]and nothing appear.
我试过，$v[0]没有出现。
is there a trick or something am I missing?
有什么技巧或我错过了什么吗？
采纳答案by Damien Pirsy
If you're talking about an associative array, you need to fetch the index directly:
如果您在谈论关联数组，则需要直接获取索引：
Example:
例子：
$array = array ('test' => 'value1', 'test2' => 'value2');
echo $array['test']; // value1
You can do a print_r($array) to see the array structure nicely formatted:
您可以执行 print_r($array) 以查看格式良好的数组结构：
<pre>
<?php print_r($array);?>
</pre>
What you're doing instead is fetch a value by its numerical index, like in
相反，您正在做的是通过其数字索引获取值，例如
$array = array('test','test2','test3');
echo $array[0]; // test
On a further note, you can check beforehand if a key exists using array_key_exists():
进一步说明，您可以使用array_key_exists()预先检查键是否存在：
var_dump(array_key_exists('test2',$array)); // (bool) TRUE
回答by Somnath Muluk
回答by Xunnamius
I believe you're looking for this: http://php.net/manual/en/function.array-keys.php
我相信你正在寻找这个：http: //php.net/manual/en/function.array-keys.php
Try (from the above page):
尝试（从上面的页面）：
<?php
$array = array(0 => 100, "color" => "red");
print_r(array_keys($array));
$array = array("blue", "red", "green", "blue", "blue");
print_r(array_keys($array, "blue"));
$array = array("color" => array("blue", "red", "green"),
"size" => array("small", "medium", "large"));
print_r(array_keys($array));
?>
回答by Drew
If you're using the foreachloop then you're probably using an associative array (i.e. $v['inputName']) So, using $v[0]wouldn't work because the indexes aren't defined by numbers - they are defined by lettering. You could use a foreachloop to then associate all the values to the numbered indexes and then us it like that.
如果您正在使用foreach循环，那么您可能正在使用关联数组（即$v['inputName']）因此，使用$v[0]将不起作用，因为索引不是由数字定义的——它们是由字母定义的。您可以使用foreach循环将所有值关联到编号索引，然后像这样使用它。
$x = array();
foreach($v as $key=>$value) {
$x[count($x)] = $key;
}
echo $x[0];
In that case $x[0]would work
在那种情况下$x[0]会起作用
回答by Nishu Tayal
You can use php array_keysfunction to get all keys. If Its Associative Array,
您可以使用 php array_keys函数来获取所有键。如果它的关联数组，
$array = array("color" => array("blue", "red", "green"),
"size" => array("small", "medium", "large"));
print_r(array_keys($array));
output will be :
输出将是：
Array
(
[0] => color
[1] => size
)
Other way is :
其他方式是：
if(is_array($v){
foreach($v as $k=>$value) {
echo "<br/>". $k ; // $k is the key
}
}
