How to determine whether array key element exists in php

In PHP, there are many ways to determine whether the key element in the array exists. This article will introduce three commonly used methods.

Method 1: Use isset() function

isset() function is used to check whether a variable has been defined and is not NULL. We can use the isset() function to determine whether the key in the array exists. An example is as follows:

// 定义一个数组
$arr = array(
    'name' => '张三',
    'age'  => 25,
    'sex'  => '男'
);

// 判断数组中的 key 是否存在
if (isset($arr['name'])) {
    echo '姓名存在';
} else {
    echo '姓名不存在';
}

Method 2: Use array_key_exists() function

array_key_exists() function is used to check whether the specified key name exists in the array. We can use the array_key_exists() function to determine whether the key in the array exists. Examples are as follows:

// 定义一个数组
$arr = array(
    'name' => '张三',
    'age'  => 25,
    'sex'  => '男'
);

// 判断数组中的 key 是否存在
if (array_key_exists('name', $arr)) {
    echo '姓名存在';
} else {
    echo '姓名不存在';
}

Method 3: Use the in_array() function

The in_array() function is used to find whether a value exists in an array. We can use the in_array() function to determine whether the key in the array exists. Examples are as follows:

// 定义一个数组
$arr = array(
    'name' => '张三',
    'age'  => 25,
    'sex'  => '男'
);

// 判断数组中的 key 是否存在
if (in_array('name', array_keys($arr))) {
    echo '姓名存在';
} else {
    echo '姓名不存在';
}

The above three methods can be used to determine whether the key in the array exists, among which the isset() function is the most commonly used method. If you are judging the value in the array instead of the key, you can use the in_array() function.

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