The key to creating an associative array in PHP is to use strings as keys. 1. It can be created directly with square brackets or array() functions, such as $user = ['name' => 'Tom', 'age' => 25]; 2. It can also add elements dynamically, such as $user['gender'] = 'male'; 3. It can also be generated through database query results, such as using PDO's fetchAll(PDO::FETCH_ASSOC) method; common errors include spelling errors in key names, not quotation marks, and duplication of key names resulting in overwriting of values.
Creating an associative array in PHP is actually quite simple. The key is to understand the difference between it and index arrays: the key of the associative array is a string, not a numeric index . You can think of it as a "name as key", such as using keys such as 'name' and 'age' to store values.
Basic writing method: Direct assignment creation
The most common way is to use square brackets [] or array() functions to create:
$user = [
'name' => 'Tom',
'age' => 25,
'email' => 'tom@example.com'
]; Or use array() to write it (applicable to versions before PHP 5.3):
$user = array(
'name' => 'Tom',
'age' => 25,
'email' => 'tom@example.com'
);This method is suitable for situations where there is not much data, just write the dead key names and values.
It is also very convenient to add elements dynamically
You don't need to define all keys from the beginning, you can add new content to the array at any time:
$user['gender'] = 'male';
You can also initialize an empty array first and then gradually fill it:
$user = []; $user['name'] = 'Jerry'; $user['age'] = 30;
This is particularly common when processing form submissions and database query results, such as taking a row of records from the database and automatically assembling them into an array.
Generate an associative array from database query results
If you are getting data from a database, you usually use a method like the following:
$stmt = $pdo->query("SELECT id, name, age FROM users");
$users = $stmt->fetchAll(PDO::FETCH_ASSOC); In this way, $users is a two-dimensional associative array, and each row has keys such as id , name and age . This format is very convenient when displaying tables and doing JSON output.
Note: If you are using mysqli, remember to use
mysqli_fetch_assoc()to ensure that you are getting an associative array, not a numeric index array.
Common error reminders
- Key name misspelling : For example,
'nmae'instead of'name', there will be no errors when running, but problems are prone to problems. - Key names are not quoted : Although PHP can sometimes be automatically recognized, it is best to add single or double quotes to avoid potential errors.
- Repeat override value for key name : the same key is assigned multiple times, and the subsequent value will overwrite the previous one.
Basically that's it. Associated arrays are one of the most basic and commonly used structures in PHP development. They are very easy to use after getting familiar with them.
The above is the detailed content of how to create an associative php array. For more information, please follow other related articles on the PHP Chinese website!
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