Common uses of array_filter include filtering empty values, filtering elements by condition, processing associative arrays, and preserving original key names. 1. Filter empty values: remove false values ??by default, such as null, empty string, 0 and false; 2. Filter by condition: If you select numbers greater than 10; 3. Process associative arrays: If you filter users older than 30; 4. Keep the original key name: If you need continuous indexing, you need to call array_values ??manually. Mastering these usages can improve data processing efficiency.
array_filter is a very practical function in PHP to filter elements in an array. Its basic logic is to use a callback function to determine which elements need to be retained. If you want to know how to use it to solve practical problems, you need to know the following common uses.
Remove empty values ??or invalid data
This is one of the most common uses of array_filter . By default, if you do not pass the callback function, it will automatically remove all "false values": such as empty strings, 0, null, false, etc., which will be filtered out.
$items = [0, 1, null, '', 'hello', false]; $result = array_filter($items); // Output: [1, 'hello']
If you just want to remove null or empty strings and keep 0 and false, you have to write the callback yourself:
$result = array_filter($items, function($item) {
return $item !== null && $item !== '';
});This allows for more precise control of filtering rules.
Filter array elements by conditions
Sometimes you need to keep certain items in the array based on specific conditions. For example, select a larger than 10 from a set of numbers:
$numbers = [5, 12, 8, 15, 3];
$filtered = array_filter($numbers, function($n) {
return $n > 10;
});
// Output: [12, 15]This mode is especially useful when processing user input and data returned by the API. For example, you can remove fields that do not match the format, or only keep entries with the status "enabled".
Process associative arrays (arrays with key names)
array_filter is also applicable to associative arrays. You can also use it if you want to keep an object or array item that meets the criteria in a certain field.
For example, we have a user list that wants to find all people older than 30:
$users = [
['name' => 'Alice', 'age' => 28],
['name' => 'Bob', 'age' => 35],
['name' => 'Charlie', 'age' => 40],
];
$olderUsers = array_filter($users, function($user) {
return $user['age'] > 30;
});The result is Bob and Charlie’s information. Note that only array items that meet the conditions are retained here, and the key name structure will not be changed.
Pay attention to the issue of retaining the original key name
By default, array_filter does not reindex the array. If you want the result to be a continuous array of indexes, remember to manually add array_values :
$filtered = array_filter([10, 20, 5, 30]); $reindexed = array_values($filtered); // The index becomes 0, 1, 2...
Otherwise you may encounter some strange index jump problems, especially during subsequent traversals or JSON encoding output.
Basically that's it. By mastering these scenes, array_filter can help you save a lot of trouble.
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