foreach 循环中的数组执行错误：

Question

Someone please help me correcting the errors in this code This was the code where i am trying to find the names of the icecreams in stock

<?php
$flavors = array();
$flavors[]=array("name" => "CD" , "in_stock" => true);
$flavors[]=array("name" => "V"  , "in_stock" => true);
$flavors[]=array("name" => "S"  , "in_stock" => false);

foreach($flavors as $flavor => $value) {
if($flavor["in_stock"] == true) {
    echo $flavor["name"] . "\n";
  }
}
?>

Answer 1

Use

<?php
$flavors = array(
array("name" => "CD" , "in_stock" => true),
array("name" => "V"  , "in_stock" => true),
array("name" => "S"  , "in_stock" => false));

foreach($flavors as $flavor){
    if ($flavor['in_stock'] == true) {
        echo $flavor['name']."\n";
    }
}
?>

instead

foreach($flavors as $flavor => value){

You are using multimentionals arrays, to use your aproach (=> value):

foreach ($flavors as $flavor => $value) {
if ($value['in_stock'] == true) {
    echo $value['name']."\n";
 }
}

PHP Arrays

Answer 2

You have flat non-associative array, that means you don't need to iterate using $key => $value but just $item .

So in you case the fix is that simple:

https://ideone.com/j7RMAH

...
// foreach ($flavors as $flavor => $value) {
foreach ($flavors as $flavor) {
...

Answer 3

foreach() - foreach will additionally assign the current element's key to the $key variable on each iteration

foreach (array_expression as $key => $value)
    statement

Note: You can use any variable it's not necessary to use the variable with name $key

You are using the key for the condition $flavor["in_stock"] and same for the $flavor["name"] . You need to use $value which holding the current iteration array , correct use of foreach for your code is

foreach($flavors as $flavor => $value) {
  if($value["in_stock"] == true) {
    echo $value["name"] . "\n";
 }
}

Answer 4

Why iterate at all? One can just filter an array with a condition:

<?php

$flavors = [];
$flavors[] = ['name' => 'CD', 'in_stock' => true];
$flavors[] = ['name' => 'V',  'in_stock' => true];
$flavors[] = ['name' => 'S',  'in_stock' => false];

$inStock = array_filter($flavors, function (array $flavor) {
    return $flavor['in_stock'];
});

print_r($inStock);

$inStockFlavors = array_column($inStock, 'name');

print_r($inStockFlavors);