Why array_search doesn't work in this case?

Question

Why my in this code array_search doesn't work? I use it without $_POST and all work well. But now I can't understand.

<_php

    $arr = array(
        'Tokyo' => 'Japan',
        'Mexico City' => 'Mexico',
        'New York City' => 'USA',
        'Mumbai' => 'India',
        'Seoul' => 'Korea',
        'Shanghai' => 'China',
        'Lagos' => 'Nigeria',
        'Buenos Aires' => 'Argentina',
        'Cairo' => 'Egypt',
        'London' => 'England');

    ?>


    <!doctype html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <meta name="viewport"
              content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
        <meta http-equiv="X-UA-Compatible" content="ie=edge">
        <title>Document</title>
    </head>
    <body>
        <form method="post" action="exercise.php">
            <select name="city">
                <?php
                    foreach ($arr as $a => $b)
                    {
                        echo "<option>$a</option>";
                    }
                ?>
            </select>

            <input type="submit" value="get a city">

        </form>

        <?php
        if ($_POST)
        {
            $city=$_POST['city'];

            $country=array_search($city, $arr);

            echo "<p>$city is in $country.</p>" ;

        }
        ?>

    </body>
    </html>

I've checked type of $country and it's string, also I've tried use $_POST['city'] instead $country but it still doesn't work. What have I done wrong?

Because the city is the key not the value. Try: $country = $arr[$city]; — AbraCadaver
– AbraCadaver, Commented May 10, 2018 at 17:32

Stephen Brooks · Accepted Answer · 2018-05-10 18:08:40Z

1

array_search() does not work here, as array_search is searching the values of the array, not the keys.

As you have the key, the best option is, as Alex suggests. However you should also check the key exists first, using array_key_exists(), as you cannot guarantee the value in your $_POST will be one of the ones you are expecting which would cause an E_NOTICE to be thrown if not.

$country = (array_key_exists($city, $arr)) ? $arr[$city] : null;

array_search(), array_key_exists()

answered May 10, 2018 at 18:08

Stephen Brooks

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Comments

Alex Howansky · Accepted Answer · 2018-05-10 17:31:31Z

0

You don't need array_search(), just use the index value directly:

$city = $_POST['city'];
$country = $arr[$city];
echo "<p>$city is in $country.</p>" ;

answered May 10, 2018 at 17:31

Alex Howansky

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