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<?php $fruits = array("d" => "lemon", "a" => "orange", "b" => "banana", "c" => "apple"); function test_alter(&$item1, $key, $prefix) { $item1 = "$prefix: $item1"; } function test_print($item2, $key) { echo "$key. $item2<br />\n"; } echo "Before ...:\n"; array_walk($fruits, 'test_print'); array_walk($fruits, 'test_alter', 'fruit'); echo "... and after:\n"; array_walk($fruits, 'test_print'); ?>
Output for 4.3.0 - 5.6.29, hhvm-3.10.0 - 3.13.2, 7.0.0 - 7.1.0
Before ...: d. lemon<br /> a. orange<br /> b. banana<br /> c. apple<br /> ... and after: d. fruit: lemon<br /> a. fruit: orange<br /> b. fruit: banana<br /> c. fruit: apple<br />