PHP函数 extract()

今天看代码，看到这个函数发现没有见过，泪奔啊说说这个函数的用法
extract(array,extract_rules,prefix)

$a = 'Original';$my_array = array("a" => "Cat","b" => "Dog", "c" => "Horse");extract($my_array);echo "\$a = $a; \$b = $b; \$c = $c";

上面会将$a直接覆盖，重新赋值

一般是将查询结果直接输出来直接可以用这个字段名

<?php$a = 'Original';$my_array = array("a" => "Cat","b" => "Dog", "c" => "Horse");extract($my_array, EXTR_PREFIX_SAME, 'dup');echo "\$a = $a; \$b = $b; \$c = $c; \$dup_a = $dup_a;";?>

上面输出的是

$a = Original; $b = Dog; $c = Horse; $dup_a = Cat;函数第二个和第三个参数都是可选参数