How to Convert an Array of Strings to Lowercase in PHP?

In PHP, you can make all strings in an array of strings lowercase by calling the strtolower() function on every element of the array using array_map(), for example, like so:

// PHP 7.4+
$arr = ['FOO', 'Bar', 'bAz'];
$newArr = array_map(fn ($str) => strtolower($str), $arr);

var_dump($newArr); // ['foo', 'bar', 'baz']

You can rewrite the callback to array_map() without arrow function to make it compatible with earlier versions of PHP.

The code above would create a new array with all strings in the array in lowercase. You can achieve the same with a simple for loop as well:

$arr = ['FOO', 'Bar', 'bAz'];
$newArr = [];

foreach ($arr as $str) {
    $newArr[] = strtolower($str);
}

var_dump($newArr); // ['foo', 'bar', 'baz']