PHP determines that the array has no keys

In PHP programming, array is a very common data type. It can store multiple data elements and access the elements through key-value pairs. When using arrays, sometimes it is necessary to determine whether a certain key exists in the array, but what should be done if the key does not exist in the array? This article will introduce several methods to determine that an array has no keys.

1. Use the in_array() function

The in_array() function is a function used in PHP to determine whether an element is in an array. When the element is in the array, the function returns true ( 1), otherwise false(0) is returned. Therefore, when we need to determine whether a certain key exists in the array, we can use the reverse result of the in_array() function to determine.

Sample code:

 'Tom', 'age' => 20, 'gender' => 'male'); if (!in_array('name', array_keys($arr))) { echo '数组中不存在该键。'; } else { echo '数组中存在该键。'; } ?>

Code analysis:

In this sample code, we use the in_array() function to determine whether 'name' is in the key array array_keys( of the $arr array) $arr), if not, output "The key does not exist in the array.", otherwise output "The key exists in the array.".

2. Use array_key_exists() function

array_key_exists() function is a function used in PHP to determine whether a certain key exists in an array. The return value of this function is true or false. This function returns true when the key exists, false otherwise.

Sample code:

 'Tom', 'age' => 20, 'gender' => 'male'); if (!array_key_exists('name', $arr)) { echo '数组中不存在该键。'; } else { echo '数组中存在该键。'; } ?>

Code analysis:

In this sample code, we use the array_key_exists() function to determine whether 'name' is in the $arr array. If not, Then output "The key does not exist in the array.", otherwise output "The key exists in the array.".

3. Use the isset() function

isset() function is also a commonly used function in PHP to determine whether a variable or array has been set. This function returns true when the specified variable or array element is set and non-null; otherwise, it returns false.

Sample code:

 'Tom', 'age' => 20, 'gender' => 'male'); if (!isset($arr['name'])) { echo '数组中不存在该键。'; } else { echo '数组中存在该键。'; } ?>

Code analysis:

In this sample code, we use the isset() function to determine whether the 'name' key in the $arr array has been set. If not set, output "The key does not exist in the array.", otherwise output "The key exists in the array.".

It should be noted that when using the isset() function to determine a key that does not exist in the array, the function will return false, which is different from the array_key_exists() function.

To sum up, the method to determine that an array has no keys in PHP is relatively simple. You can use the in_array() function, array_key_exists() function or isset() function, etc. In actual use, you can choose a suitable method based on your needs and personal habits.

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