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在本文中，我们将介绍查找 foreach 索引的方法。

• 使用 key 变量
• 使用 index 变量
• 同时使用 key 和 index 变量

在 PHP 中使用 key 变量查找 foreach 索引

变量键将每个值的索引存储在 foreach 循环中。PHP 中的 foreach 循环按如下方式使用。

foreach($arrayName as $value){
    //code
}

变量值存储数组中每个元素的值。

<?php 
$array = array(1, 2, 3, 4, 5, 6, 7, 8, 9, 10); 

foreach ($array as $key => $value) {
    echo "The index is = " . $key . ", and value is = ". $value; 
    echo "\n";
}   
?>

这里的关键变量包含 foreach 循环的索引。变量值显示数组中每个元素的值。

输出：

The index is = 0, and the value is = 1
The index is = 1, and the value is = 2
The index is = 2, and the value is = 3
The index is = 3, and the value is = 4
The index is = 4, and the value is = 5
The index is = 5, and the value is = 6
The index is = 6, and the value is = 7
The index is = 7, and the value is = 8
The index is = 8, and the value is = 9
The index is = 9, and the value is = 10

在 PHP 中使用 index 变量查找 foreach 索引

变量索引用作附加变量，以显示每次迭代中 foreach 的索引。

<?php 
// Declare an array 
$arr = array(1, 2, 3, 4, 5, 6, 7, 8, 9, 10); 
$index = 0;

foreach($arr as $key=>$val) {
    echo "The index is $index";
    $index++;
    echo "\n";
}
?>

输出：

The index is 0
The index is 1
The index is 2
The index is 3
The index is 4
The index is 5
The index is 6
The index is 7
The index is 8
The index is 9

在 PHP 中同时使用 key 和 index 变量查找 foreach 索引

现在，我们将同时使用 key 变量和附加变量 index 来查找 foreach 的索引。

<?php 
  
// Declare an array 
$arr = array(1, 2, 3, 4, 5, 6, 7, 8, 9, 10); 
$index = 0;

foreach ($arr as $key=>$value) {
    echo "The index is $index";
    $index = $key+1;
    echo "\n";
}
  
?>

我们已将 key 变量的值存储为索引 index 变量中其值的增量。这样，我们既可以使用 key 变量又可以使用 index 变量来查找 foreach 的索引。

输出：

The index is 0
The index is 1
The index is 2
The index is 3
The index is 4
The index is 5
The index is 6
The index is 7
The index is 8
The index is 9