What exactly does the in_array function do?’
时间: 2023-11-27 20:49:18 浏览: 53
The `in_array` function is a built-in function in PHP that checks if a value exists in an array. It takes two arguments: the first argument is the value you want to search for, and the second argument is the array you want to search in.
The function returns `true` if the value is found in the array, and `false` otherwise. Here's an example:
```
$fruits = array("apple", "banana", "orange");
if (in_array("banana", $fruits)) {
echo "Found banana!";
} else {
echo "Could not find banana :(";
}
```
In this example, the `in_array` function is used to check if the value "banana" exists in the `$fruits` array. Since "banana" is in the array, it will output "Found banana!".
相关问题
What exactly do the array_keys and array_values functions do?
The `array_keys()` function in PHP returns all the keys of an array as a new array. It takes an array as an argument and returns an array of keys.
Example:
```php
$array = array('key1' => 'value1', 'key2' => 'value2');
$keys = array_keys($array);
print_r($keys);
```
Output:
```
Array
(
[0] => key1
[1] => key2
)
```
The `array_values()` function in PHP returns all the values of an array as a new array. It takes an array as an argument and returns an array of values.
Example:
```php
$array = array('key1' => 'value1', 'key2' => 'value2');
$values = array_values($array);
print_r($values);
```
Output:
```
Array
(
[0] => value1
[1] => value2
)
```
Both of these functions are useful for manipulating arrays in PHP.
What is the purpose of the PHP mysql_select_db function?
The purpose of the PHP `mysql_select_db` function is to select a MySQL database to work with. This function sets the current active database on the MySQL connection specified by the `link_identifier` parameter. Once a database is selected, all subsequent queries will be executed on that database until a new database is selected with `mysql_select_db` or a new connection is established.
The syntax for the `mysql_select_db` function is as follows:
```
bool mysql_select_db ( string $database_name [, resource $link_identifier ] )
```
Here, the `database_name` parameter specifies the name of the database to select, and the optional `link_identifier` parameter is a MySQL connection identifier returned by `mysql_connect`. If the `link_identifier` parameter is not specified, the last opened connection is used.
It is important to note that the `mysql_*` functions are deprecated in PHP 5.5.0 and removed in PHP 7.0.0. It is recommended to use MySQLi or PDO_MySQL extensions instead.
相关推荐
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)