mysqli_fetch_assoc() 和PDO::fetch() 的主要區(qū)別在於擴展和功能靈活性。 1. mysqli_fetch_assoc() 是mysqli 擴展的一部分，僅支持MySQL 數(shù)據(jù)庫，返回結果為關聯(lián)數(shù)組；2. PDO::fetch() 屬於更通用的PDO 擴展，支持多種數(shù)據(jù)庫，並可通過參數(shù)設置返回類型如關聯(lián)數(shù)組(PDO::FETCH_ASSOC)、數(shù)字數(shù)組(PDO::FETCH_NUM)或對象(PDO::FETCH_OBJ)；3. 使用mysqli 時需手動釋放結果集，而PDO 會在語句對象超出作用域後自動處理；4. PDO 提供更多高級功能如預處理語句和麵向對象接口，適合大型應用開發(fā)。

When you're working with PHP and need to retrieve data from a MySQL database, mysqli_fetch_assoc() and PDO::fetch() are two common functions used to fetch rows from a result set. Both do similar jobs but in slightly different ways depending on whether you're using the older mysqli extension or the more flexible PDO (PHP Data Objects).

Here's how to use both effectively.

Using mysqli_fetch_assoc() – Get Rows as Associative Arrays

Once you've executed a query using mysqli_query() , you can loop through the results using mysqli_fetch_assoc() . It returns each row as an associative array where the keys are column names.

 $result = mysqli_query($connection, "SELECT id, name FROM users");

while ($row = mysqli_fetch_assoc($result)) {
    echo &#39;User: &#39; . $row[&#39;name&#39;] . &#39;<br>&#39;;
}

• This is great for simple scripts.
• Make sure your query was successful before fetching — always check if $result is valid.
• Each call to mysqli_fetch_assoc() moves the internal pointer forward, so it naturally stops at the end of the result set.

Note: If you're using the object-oriented style with mysqli, the syntax changes slightly:

 $result = $connection->query("SELECT id, name FROM users");
while ($row = $result->fetch_assoc()) {
// process row
}

Using PDO::fetch() – Flexible Fetching with PDO

If you're using PDO, you'll typically prepare and execute your queries first, then fetch rows using the fetch() method. By default, PDO::fetch() returns an array that's both associative and numeric ( PDO::FETCH_BOTH ), but you can change this behavior.

To get just an associative array:

 $stmt = $pdo->query("SELECT id, name FROM users");
while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
    echo &#39;User: &#39; . $row[&#39;name&#39;] . &#39;<br>&#39;;
}

Some other useful modes include:

• PDO::FETCH_NUM : numeric array only
• PDO::FETCH_OBJ : returns an anonymous object
• You can even fetch into a class with PDO::FETCH_CLASS

This flexibility makes PDO a better choice for larger applications or when working with different databases.

Common Pitfalls and Tips

• Don't mix fetching styles – Stick to one type per loop. Mixing fetch_assoc() and fetch_object() might lead to confusion or missed rows.
• Always check for errors – Especially after executing queries. In mysqli, use mysqli_error($connection) , and in PDO, enable exceptions or check error codes.
• Free your result sets – In mysqli, use mysqli_free_result($result) after you're done to free memory. With PDO, this usually happens automatically when the statement object goes out of scope.
• Use loops wisely – Both functions return false when there are no more rows, so a while loop works perfectly.

Fetching data doesn't have to be complicated. Whether you're using mysqli_fetch_assoc() or PDO::fetch() , understanding what kind of data you're getting back and how to loop through it is key. Just make sure to handle errors, clean up resources, and choose the method that best fits your project setup.

基本上就這些。

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