数组和字符串相互转化！

把数组元素组合为字符串：数组->字符串

<?php
$arr = array('Hello','World!','I','love','Shanghai!');
echo implode(" ",$arr);
?>

把字符串打散为数组：字符串->数组

<?php
$str = "Hello world. I love Shanghai!";
print_r (explode(",",$str));
?>