PHP is an open source server-side scripting language that can be used in dynamic web development, command line scripting, desktop application development and other fields. In PHP, arrays are a very important data type that can be used to store multiple values and access elements in the array through indexes or key-value pairs. This article will explore a method in PHP to determine whether an array key exists, that is, using the in_array() function and array_key_exists() function.
1. in_array() function
in_array() function is a function in PHP used to determine whether a value exists in an array. Its syntax is as follows:
bool in_array ( mixed $needle , array $haystack [, bool $strict = FALSE ] )
where , $needle is the value to be searched, $haystack is the array to be searched, $strict is an optional parameter, indicating whether to enable strict mode, the default is FALSE, which means that strict mode is not enabled.
In the in_array() function, we can set $needle to the key in the array, $haystack to the array, and then use the return value of the function to determine whether the key exists in the array. The specific code is as follows:
$my_array = array('a' => 1, 'b' => 2, 'c' => 3); if (in_array('a', array_keys($my_array))) { echo '键 a 存在'; } else { echo '键 a 不存在'; }
In the above code, we first obtain all the keys in the array through the array_keys() function, and then pass them as parameters to the in_array() function. If the return value is true , it means that the key exists in the array; otherwise, it means that the key does not exist in the array.
2. array_key_exists() function
array_key_exists() function is a function in PHP used to determine whether a key exists in an array. Its syntax is as follows:
bool array_key_exists ( mixed $key , array $array )
where , $key is the key to be searched, and $array is the array to be searched.
Use the array_key_exists() function to determine whether the key of the array exists. In fact, you can also use the in_array() function plus the array_keys() function to achieve this, but the array_key_exists() function is more concise and clear. The specific code is as follows:
$my_array = array('a' => 1, 'b' => 2, 'c' => 3); if (array_key_exists('a', $my_array)) { echo '键 a 存在'; } else { echo '键 a 不存在'; }
In the above code, we directly use the array_key_exists() function to determine whether key a exists in the array. If the return value is true , it means that the key exists in the array; otherwise, it means that the key does not exist in the array.
3. The difference between the in_array() function and the array_key_exists() function
Both the in_array() function and the array_key_exists() function can be used to determine whether the key in the array exists, but there is a difference between them There are still some differences. The details are as follows:
- When using the in_array() function to determine whether an array key exists, you need to first use the array_keys() function to obtain all the keys in the array, so some additional overhead will be added.
- The in_array() function is used to determine whether a value exists in the array, not whether a certain key exists in the array.
- array_key_exists() The code of the function is more concise and clear, so the execution efficiency may be higher.
4. Summary
In PHP, you can use the in_array() function and array_key_exists() function to determine whether an array key exists. Among them, the in_array() function needs to use the array_keys() function to obtain all the keys in the array, so it will add some additional overhead; while the code of the array_key_exists() function is more concise and clear, so the execution efficiency may be higher. In actual development, we should choose which method to use based on the actual situation.
The above is the detailed content of How to determine whether an array contains a specified key in php. For more information, please follow other related articles on the PHP Chinese website!

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