How to get subscript from php array

It is very common to use arrays in PHP. An array is a data structure that can store multiple values. When using an array, in addition to getting the values ​​in the array, you can also get the subscript of the array. The subscript refers to the address of each element in the array, and is also the position of each element in the array.

PHP provides multiple ways to obtain array subscripts, three of which will be introduced below.

1. Using foreach loop

When using foreach loop to traverse an array, each loop will assign elements in the array to variables. At this point, you can use the $key variable to get the subscript of each element in the array. The specific code is as follows:

$array = array('a' => 1, 'b' => 2, 'c' => 3); 
foreach ($array as $key => $value) { 
    echo $key."<br>"; 
}

The above code will output the subscripts of the array elements: a, b, c.

2. Use the array_keys() function

The array_keys() function is a function provided by PHP to obtain the array subscript. The syntax of this function is as follows:

array_keys(array $array, $search_value, $strict);

Among them, $array indicates the array of subscripts to be obtained; $search_value indicates the value of the element to be found; $strict indicates whether strict comparison is enabled. If the $search_value parameter is not passed, all subscripts of the array are returned.

The following code demonstrates how to use the array_keys() function to obtain the array subscript:

$array = array('a' => 1, 'b' => 2, 'c' => 3); 
$keys = array_keys($array); 
foreach ($keys as $key) { 
    echo $key."<br>"; 
}

The above code will output the subscripts of the array elements: a, b, c.

3. Use the array_map() function

The array_map() function is another function provided by PHP to obtain the array subscript. The syntax of this function is as follows:

array_map(callable $callback, array $array1, array ...$array2);

Among them, $callback is a callback function used to process arrays; $array1 is the array to be processed. When there is only one array, $callback will accept two parameters: one is the value of the array element, and the other is the subscript of the array element. When there are multiple arrays, $callback will accept the same number of parameters, each parameter representing an element from a different array. Finally, the array_map() function returns an array containing the processed elements.

The following code demonstrates how to use the array_map() function to obtain the array subscript:

$array = array('a' => 1, 'b' => 2, 'c' => 3); 
$keys = array_map(function($value, $key) { return $key; }, $array, array_keys($array)); 
foreach ($keys as $key) { 
    echo $key."<br>"; 
}

The above code will output the subscripts of the array elements: a, b, c.

Summary

The above three methods can be used to obtain the subscript of the PHP array. Which method to choose can be decided according to your own code situation. Whichever way you choose, you can easily get the array subscript, making it easier to manipulate PHP arrays.

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