Array_keys() function in PHP: How to get all key names in an array

In PHP, arrays are a very practical data type that allow us to store multiple values ​​in one variable. When using PHP arrays, we often need to access the key names of the array, for example, to loop through the array or get the value of a specific key. The array_keys() function allows us to simply get all the key names in the array. In this article, we will explore the application of the array_keys() function and provide specific code examples.

Basic syntax of the array_keys() function

In PHP, the array_keys() function is used to return an array of all key names in the array. The basic syntax of this function is as follows:

array array_keys ( array $array [, mixed $search_value = null [, bool $strict = false ]] )

Among them, $array represents the target array whose key name we want to obtain. $search_value Optional parameter, if this parameter is specified, array_keys() will only return key names with a value equal to $search_value. $strict is also an optional parameter, whether to perform strict comparison when comparing values. By default, this parameter is false, indicating a loose comparison.

The following is a simple example:

$my_array = array("apple" => 2, "banana" => 3, "orange" => 4);
$keys = array_keys($my_array);

print_r($keys);

Executing the above code will output:

Array
(
    [0] => apple
    [1] => banana
    [2] => orange
)

Get the key name of a specific value

We can array_keys() The second parameter $search_value is used in the function to specify the specific value whose key name we want to get. The following is an example:

$my_array = array("apple" => 2, "banana" => 3, "orange" => 2);
$keys = array_keys($my_array, 2);

print_r($keys);

Executing the above code will output:

Array
(
    [0] => apple
    [1] => orange
)

In the above example, we specified the second parameter as 2, and the result We get all the keys whose value is equal to 2.

Use the array_keys() function for array operations

array_keys() The function can not only be used to simply obtain the key name of the array, but can also be used in combination with other array functions Perform more complex operations. Below are some code examples that demonstrate different uses of the array_keys() function.

Delete specific keys in the array

We can use the array_diff() function to delete certain key names in the array. First, we use the array_keys() function to get the array of keys we want to delete. Next, we can use the array_diff() function to delete them from the array. The following is a sample code:

$my_array = array("apple" => 2, "banana" => 3, "orange" => 4);
$keys_to_remove = array_keys($my_array, 2);
$my_array = array_diff_key($my_array, array_flip($keys_to_remove));

print_r($my_array);

The above code will output:

Array
(
    [banana] => 3
    [orange] => 4
)

In the above code, we first use the array_keys() function to obtain all values ​​equal to The key name of 2, the result is ["apple", "orange"]. Then, we use the array_flip() function to flip the key array, so that we can use the array_diff_key() function to perform the key difference operation on the original array to obtain only the key name array containing ["banana", "orange"] Array of key names.

Count the number of all keys in the array

We can use the count() function to count the number of all keys in the array. The following is a sample code:

$my_array = array("apple" => 2, "banana" => 3, "orange" => 4);
$keys_count = count(array_keys($my_array));

echo "The total number of keys in the array is: " . $keys_count;

The above code will output:

The total number of keys in the array is: 3

In the above code, we use the array_keys() function to get all the key names, and then Use the count() function to count the number of key names, and finally output the result.

Summary

In this article, we introduced the basic syntax of the array_keys() function in PHP, and how to get the key name of a specific key value, which is useful for some practical Very useful for programming tasks. We also demonstrated how to use the array_keys() function to perform more complex array operations. I hope readers can master these techniques and apply them to actual projects.

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