PHP query key value in array

In the PHP development process, array processing is a very common operation. When we need to query a certain key value in an array, PHP provides a variety of methods to achieve this purpose. This article will introduce several commonly used methods to query key values ​​​​in arrays.

1. Use the array_key_exists function to query the key value

array_key_exists is a built-in function in PHP, used to determine whether the specified key name or index exists in the array.

The following is a code example of using the array_key_exists function to query the key value:

$arr = array('name' => '张三', 'age' => 18, 'gender' => '男');

if (array_key_exists('name', $arr)) {
    echo $arr['name']; // 输出：张三
} else {
    echo '不存在该键名';
}

In the above code, an associative array $arr is first defined, and then the array_key_exists function is used to query whether it exists in the array Key with keyname 'name'. If it exists, the value corresponding to the key is output, otherwise a prompt message is output.

2. Use the in_array function to query key values

in_array is a built-in function in PHP, used to determine whether a value exists in an array.

The following is a code example of using the in_array function to query the key value:

$arr = array('张三', '李四', '王五');

if (in_array('李四', $arr)) {
    echo '存在'; // 输出：存在
} else {
    echo '不存在';
}

In the above code, an index array $arr is first defined, and then the in_array function is used to query whether it exists in the array The element whose value is 'John Doe'. If it exists, a prompt message is output, otherwise another prompt message is output.

3. Use the array_search function to query key values

array_search is a built-in function in PHP, used to search for a specified value in an array and return the key name corresponding to the value.

The following is a code example that uses the array_search function to query key values:

$arr = array('name' => '张三', 'age' => 18, 'gender' => '男');

$key = array_search('张三', $arr);

if ($key !== false) {
    echo $key; // 输出：name
} else {
    echo '不存在该值';
}

In the above code, an associative array $arr is first defined, and then the array_search function is used to query the value of the array. The key name corresponding to the element of 'Zhang San'. If it exists, the key name is output, otherwise a prompt message is output.

It should be noted that the array_search function has a return value. When the search fails, the function will return false, so when judging the search results, strict comparison symbols need to be used.

Conclusion

The above are several ways to use PHP to query the key values ​​​​in an array. In actual development, you can choose a method that suits you according to specific needs. At the same time, there are some other functions, such as array_keys, array_values, etc., which can also be used to query the keys or values ​​in the array. Readers can learn about them by themselves.

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