How to return a key value of an array in php

PHP is a scripting language that is ideal for web development. In PHP, an array is a very common data structure whose main feature is that it can store multiple values ​​and these values ​​can be accessed through keys. In this article, we will show you how to return a key value of an array.

In PHP, it is very simple to return a key value of an array. You only need to use the array name followed by square brackets. The square brackets contain the key value that needs to be returned. For example:

<?php
// 定义一个包含多个键值的数组
$arr = array(
    &#39;name&#39; => 'Tom',
    'age' => 20,
    'sex' => 'male'
);

// 返回数组的一个键值
echo $arr['name']; // 输出 Tom
?>

The above code defines an associative array containing multiple key values, and then use $arr['name'] to return the value corresponding to the 'name' key in the array, which is 'Tom '. It should be noted here that if the accessed key does not exist, PHP will return a Notice level warning.

In addition to using square brackets to return a key value, we can also use some built-in functions provided by PHP to operate on arrays. Below we will introduce several commonly used functions.

1. array_key_exists()

The array_key_exists() function is used to check whether an array contains the specified key name. Returns true if included, false otherwise. For example:

<?php
// 定义一个包含多个键值的数组
$arr = array(
    &#39;name&#39; => 'Tom',
    'age' => 20,
    'sex' => 'male'
);

// 检查数组中是否包含指定的键名
if (array_key_exists('age', $arr)) {
    echo '数组中包含age键';
} else {
    echo '数组中不包含age键';
}
?>

In the above code, use the array_key_exists() function to check whether the $arr array contains the 'age' key. Because this key exists in the array, the output is "the array contains the age key" .

2. array_keys()

The array_keys() function is used to return all the key names in an array. For example:

<?php
// 定义一个包含多个键值的数组
$arr = array(
    &#39;name&#39; => 'Tom',
    'age' => 20,
    'sex' => 'male'
);

// 返回数组中所有的键名
$keys = array_keys($arr);
print_r($keys);
?>

In the above code, the array_keys() function is used to return all the key names in the $arr array, and the print_r() function is used to output the result. The result is:

Array
(
    [0] => name
    [1] => age
    [2] => sex
)

3. array_values ()

array_values() function is used to return all the values ​​in an array. For example:

<?php
// 定义一个包含多个键值的数组
$arr = array(
    &#39;name&#39; => 'Tom',
    'age' => 20,
    'sex' => 'male'
);

// 返回数组中所有的值
$values = array_values($arr);
print_r($values);
?>

In the above code, the array_values() function is used to return all the values ​​in the $arr array, and the print_r() function is used to output the result. The result is:

Array
(
    [0] => Tom
    [1] => 20
    [2] => male
)

4. in_array( )

in_array() function is used to check whether a value exists in an array. Returns true if present, false otherwise. For example:

<?php
// 定义一个包含多个值的数组
$arr = array(&#39;a&#39;, &#39;b&#39;, &#39;c&#39;, &#39;d&#39;, &#39;e&#39;);

// 检查一个值是否存在于数组中
if (in_array(&#39;c&#39;, $arr)) {
    echo &#39;数组中包含c值&#39;;
} else {
    echo &#39;数组中不包含c值&#39;;
}
?>

In the above code, the in_array() function is used to check whether a value exists in the $arr array. Because this value exists in the array, the output is "the array contains the c value".

The above four functions are commonly used array functions in PHP. Mastering their use is very helpful for processing array data.

Finally, it should be noted that if you want to return multiple key values ​​in the array, you can use a foreach loop to traverse the array to obtain all the required key values. The above is the content of this article on how PHP returns a key value of an array. I hope this article can be helpful to readers.

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