How to determine whether an array contains a specified key in php

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:

1. 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.
2. The in_array() function is used to determine whether a value exists in the array, not whether a certain key exists in the array.
3. 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.

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