Let's talk about how to modify the keys in a two-dimensional array in PHP

PHP two-dimensional array is an array composed of multiple one-dimensional arrays, where each one-dimensional array contains multiple elements. When processing such an array, sometimes we need to modify the keys in the two-dimensional array to meet our business needs. This article will introduce how to modify the keys in a two-dimensional array in PHP.

1. Modify the specified keys of all sub-arrays

Sometimes, we need to modify the specified keys of all sub-arrays in a two-dimensional array to a new key name. You can use the array_map function to do this accomplish. The array_map function can apply a custom function to each element of the array.

The following is a code example:

function changeKey($arr, $oldkey, $newkey){
    if(!is_array($arr)){
        return $arr;
    }
    $result = array();
    foreach($arr as $key=>$val){
        if(is_array($val)){
            $result[$key] = changeKey($val, $oldkey, $newkey);
        } else {
            $result[$key] = $val;
            if($key == $oldkey){
                $result[$newkey] = $val;
                unset($result[$oldkey]);
            }
        }
    }
    return $result;
}

$oldArray = array(
    array('id'=>1, 'name'=>'php', 'type'=>'backend'),
    array('id'=>2, 'name'=>'js', 'type'=>'frontend')
);

$newArray = array_map(function($arr){
    return changeKey($arr, 'type', 'category');
}, $oldArray);

print_r($newArray);

The above code changes the 'type' key in all sub-arrays in $oldArray to the 'category' key. The output result is as follows:

Array
(
    [0] => Array
        (
            [id] => 1
            [name] => php
            [category] => backend
        )

    [1] => Array
        (
            [id] => 2
            [name] => js
            [category] => frontend
        )

)

2. Modify the specified key of the specified sub-array

Sometimes, we only need to modify the specified key of a certain sub-array in the two-dimensional array. You can directly modify the sub-array. Array to achieve. The following is a code example:

$oldArray = array(
    array('id'=>1, 'name'=>'php', 'type'=>'backend'),
    array('id'=>2, 'name'=>'js', 'type'=>'frontend')
);

foreach($oldArray as &$arr){
    if($arr['id'] == 1){
        $arr['type'] = 'server side';
    }
}

print_r($oldArray);

The above code changes the 'type' key of the subarray with $id 1 in $oldArray to 'server side'. The output results are as follows:

Array
(
    [0] => Array
        (
            [id] => 1
            [name] => php
            [type] => server side
        )

    [1] => Array
        (
            [id] => 2
            [name] => js
            [type] => frontend
        )

)

3. Conclusion

PHP two-dimensional array is one of the data structures widely used in PHP. Once you master the method of modifying the keys in the PHP two-dimensional array, you can easily do it data processing. This article introduces two methods of modifying keys in PHP two-dimensional arrays through examples. I hope it will be helpful to everyone.

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