php中利用explode函数分割字符串到数组

<?php 
$source = "hello1,hello2,hello3,hello4,hello5";//按逗号分离字符串 
$hello = explode(',',$source); 

for($index=0;$index<count($hello);$index++) 
{ 
echo $hello[$index];echo "</br>"; 
} 
?> 

<?php 
$date = "04/30/1973"; 
list($month, $day, $year) = split ('[/.-]', $date); 
echo "Month: $month; Day: $day; Year: $year<br />\n"; 
?> 

<?php
$keyword="asp php,jsp";
$keyword=str_replace("  "," ",$keyword);
$keyword=str_replace(" ",",",$keyword);
$keyarr=explode(',',$keyword); 
for($index=0;$index<count($keyarr);$index++) 
{ 
$whereSql .= " And (arc.title like '%$keyarr[$index]%' Or arc.keywords like '%$keyarr[$index]%') ";
} 
echo $whereSql;