Using built-in functions as callbacks

In functions taking callable as an argument, you can also put a string with PHP built-in function. It’s common to use trim as array_map parameter to remove leading and trailing whitespace from all strings in the array.

$arr = ['   one  ', 'two   ', '   three'];
var_dump(array_map('trim', $arr));

// array(3) {
//   [0] =>
//   string(3) "one"
//   [1] =>
//   string(3) "two"
//   [2] =>
//   string(5) "three"
// }