3d嵌套数组foreach语句问题

Question

I have this array written below, and I know it isnt pretty, sorry. I come to this array structure as it is the only way I could think of when dealing with my post request.

$_POST = array("person" => array(
                                 [1] => array("id" => 1, "name" => "bob"), 
                                 [2] => array("id" => 2, "name" => "jim")
                                )
               );

I want to be able to pick "name" from certain "id", so below code is what I came up with. In the example below, if person["id"] is equal to 1, retrieve its "name" which is "bob".

foreach ($_POST as $dataSet) {
    foreach ($dataSet as $person) {
        foreach ($person as $field => $value) {
            if ($person["id"] == 1) {
                echo $person["name"];
            }
        }
    }
}

The problem I am having is as I execute the code. the result is bobbob ,

it seems like the code looped the if statement twice (same as the number of elements in the person array). I know if I put break into the code, then it will solve it, but anyone know why it looped twice? Maybe this will deepen my foreach and array understanding.

Answer 1

There is no need to have third nested loop . Hope this one will be helpful.

Problem: In the third loop you were iterating over Persons: array("id" => 1, "name" => "bob") which have two keys. and you are checking only single static key $person["id"] , that's why it was printing twice.

Solution 1:

Try this code snippet here

<?php

ini_set('display_errors', 1);

$POSTData = array("person" => array(
        1 => array("id" => 1, "name" => "bob"),
        2 => array("id" => 2, "name" => "jim")
    )
);
foreach ($POSTData as $dataSet)
{
    foreach ($dataSet as $person)
    {
        if ($person["id"] == 1)
        {
            echo $person["name"];
        }
    }
}

Solution 2:

Alternatively you can try this single line solution.

Try this code snippet here

 echo array_column($POSTData["person"],"name","id")[1];//here 1 is the `id` you want.

Answer 2

No need of third foreach

 <?php
   $mainArr = array("person" => array(
                        1 => array("id" => 1, "name" => "bob"), 
                        2 => array("id" => 2, "name" => "jim")
                           )
                   );
   foreach ($mainArr as $dataSet) {
       foreach ($dataSet as $person) {
         if ($person["id"] == 1) {
             echo $person["name"];
             break;
         }
       }
   }

   ?>

Live demo : https://eval.in/855386

Answer 3

You must have seen the other answers, and they have already said that you dont need the 3rd loop . but still if you want to keep the third loop. you can use this code.

foreach ($_POST as $dataSet) {

    foreach ($dataSet as $person) {

        foreach ($person as $field => $value) {

            if($value == 1){
                echo $person['name'];
            }

        }

    }

}

Answer 4

Although it's unclear why you need to do a POST in this fashion, here's how to get "bob" only once:

<?php

$_POST = array("person" => array(
                                 1 => array("id" => 1, "name" => "bob"), 
                                 2 => array("id" => 2, "name" => "jim")
                                )
               );



$arr = array_pop($_POST);

foreach($arr as $a) {
  if ($a["id"] == 1) {
    echo $a["name"];
  }
}

Array_pop() is useful for removing the first element of the array whose value is an array itself which looks like this:

array(2) {
  [1]=>
  array(2) {
    ["id"]=>
    int(1)
    ["name"]=>
    string(3) "bob"
  }
  [2]=>
  array(2) {
    ["id"]=>
    int(2)
    ["name"]=>
    string(3) "jim"
  }
}

When the if conditional evaluates as true which occurs only once then the name "bob" displays.

See live code .

Alternatively, you could use a couple of loops as follows:

foreach ($_POST["person"] as $data) {
    foreach ($data as $value) {
        if ( $value == 1) {
            echo $data["name"],"\n";
        }
    }
}

See demo

Answer 5

As you mentioned, I want to be able to pick name from certain id, : No need of nested looping for that. You can do like this using array_column and array_search :

$data = array("person" => array(
        1 => array("id" => 1, "name" => "bob"),
        2 => array("id" => 2, "name" => "jim")
    )
);

// 1 is id you want to search for
$key = array_search(1, array_column($data['person'], 'id'));
echo $data['person'][$key + 1]['name']; // $key + 1 as you have started array with 1

Output:

bob

with foreach:

foreach ($data as $dataValue) {
    foreach ($dataValue as $person) {
        if ($person['id'] === 1) {
            echo $person["name"];
        }
    }
}