php 利用array_slice函数获取随机数组或前几条数据

$input = array("a", "b", "c", "d", "e");
$output = array_slice($input, );  //返回下标开始的数组 returns "c", "d", and "e"
$output = array_slice($input, -, ); // returns "d"
$output = array_slice($input, , ); // returns "a", "b", and "c"
// note the differences in the array keys
print_r(array_slice($input, , -));
print_r(array_slice($input, , -, true));

<?php
$a=array(0=>"Dog",1=>"Cat",2=>"Horse",3=>"Bird");
print_r(array_slice($a,1,2));
?>

<?php
$a=array(0=>"Dog",1=>"Cat",2=>"Horse",3=>"Bird");
print_r(array_slice($a,-2,1));
?>

<?php
$a=array(0=>"Dog",1=>"Cat",2=>"Horse",3=>"Bird");
print_r(array_slice($a,1,2,true));
?>

<?php
$a=array("a"=>"Dog","b"=>"Cat","c"=>"Horse","d"=>"Bird");
print_r(array_slice($a,1,2));
?>