foreach.php

<?php

$arr = 'GIF','JPG','PNG','SWF','PSD'];

// foreach ($arr as $value){

//     $temp[] = strtolower($value);

// }

// print_r($temp);

$arr = array_map('strtolower',$arr);

print_r($array);

// 1 internal operations can traverse the array automatic

2 // Data type of the second parameter is an array, the array will in turn pass the value to the first parameter

// callback function: it refers to the function name as a parameter to another function appears