PHP: remove element from multidimensional array (by key) using foreach

问题

I got multidimensional array. From each subarray, I would like to remove / unset values with index 1. My array $data.

Array
(
    [3463] => Array
        (
            [0] => 1
            [1] => 2014
            [context] => 'aaa'
        )

    [3563] => Array
        (
            [0] => 12
            [1] => 2014
            [context] => 'aaa'
        )       

    [2421] => Array
        (
            [0] => 5
            [1] => 2014
            [context] => 'zzz'
        )               
)

I would like to remove every element with index '1' from subarrays. Desired output is:

Array
(
    [3463] => Array
        (
            [0] => 1
            [context] => 'aaa'
        )

    [3563] => Array
        (
            [0] => 12
            [context] => 'aaa'
        )       

    [2421] => Array
        (
            [0] => 5
            [context] => 'zzz'
        )               
)

Why this does not work?

foreach ($data as $subArr) {
   foreach ($subArr as $key => $value) {
       if ($key == '1') {
        unset($subArr[$key]);
       }

   }
}

I'm sorry if this problem is trivial for you guys.

回答1:

easy way!? you can do this just with one foreach!

foreach ($data as $key => $subArr) {
    unset($subArr['1']);
    $data[$key] = $subArr;  
}

回答2:

you are making changes in subarray instead of main one try this may help

foreach ($data as $key => $subArr) { 
    unset($data[$key][1]);      
}

回答3:

It does not work because $subArr from the outer foreach contains copies of the values of $data and the inner foreach modifies these copies, leaving $data not touched.

You can fix that by telling PHP to make $subArr references to the original values stored in $data:

foreach ($data as &$subArr) {
   foreach ($subArr as $key => $value) {
       if ($key == '1') {
        unset($subArr[$key]);
       }
   }
}

Another option is to use function array_map(). It uses a callback function that can inspect (and modify) each value of $data and it returns a new array.

$clean = array_map(
    function (array $elem) {
        unset($elem['1']);        // modify $elem
        return $elem;             // and return it to be put into the result
    },
    $data
);

print_r($clean);

回答4:

try this:

<?php 
    $data = Array
    (
        '3463' => Array
            (
                '0' => 1,
                '1' => 2014,
                'context' => 'aaa'
            ),

        '3563' => Array
            (
                '0' => 12,
                '1' => 2014,
                'context' => 'aaa'
            ),       

        '2421' => Array
            (
                '0' => 5,
                '1' => 2014,
                'context' => 'zzz'
            )               
    );

    foreach ($data as $k=>$subArr) {
        foreach ($subArr as $key => $value) {

            if ($key == '1') {
                unset($data[$k][$key]);
            }

        }
    }
print_r($data);// display the output

来源：https://stackoverflow.com/questions/27482851/php-remove-element-from-multidimensional-array-by-key-using-foreach

标签

php

arrays

multidimensional-array

foreach

unset