php的代码重用与函数

<?php
//使用require()、include()函数
echo 'This is the main file.<br/>';
require('reusable.php');
echo 'The script will end now.<br/>';
//函数声明
function my_function(){
echo 'My function was called';
}
my_function();
//使用参数
function create_table($data){
echo "<table border=\"1\">";
reset($data);
$value=current($data);
while($value){
echo "<tr><td>".$value."</td></tr>\n";
$value=next($data);
}
echo "</table>";
}
$my_array=array('Line one','Line two','Line three');
create_table($my_array);
//作用域 关键字global
function fn(){
global $var;
$var="contens 2";
echo "inside the function,\$var =".$var."<br/>";
}
$var="contents 1";
fn();
echo "outside the function,\$var =".$var."<br/>";
//参数的引用传递和值传递：地址符&
function increment(&$value,$amount=1){
$value=$value+$amount;
}
$a=10;
echo $a.'<br/>';
increment($a);
echo $a.'<br/>';
//return关键字：终止函数的执行
function larger($x,$y){
if((!isset($x))||(!isset($y))){
echo "This function requires two numbers.<br/>";
return;
}
if($x>=$y){
echo $x."<br/>";
}else{
echo $y."<br/>";
}
}
$a=1;
$b=2.5;
$c=1.9;
larger($a,$b);
larger($d,$a);
//return关键字：从函数返回一个值
function smaller($x,$y){
if((!isset($x))||(!isset($y))){
return false;
}else if($x<=$y){
return $x;
}else{
return $y;
}
}
echo smaller($a,$b).'<br/>';
echo smaller($d,$a).'<br/>';
//实现递归
function reverse_r($str){
if(strlen($str)>0){
reverse_r(substr($str,1));
}
echo substr($str,0,1);
return;
}
function reverse_i($str){
for($i=1;$i<=strlen($str);$i++){
echo substr($str,-$i,1);
}
return;
}
reverse_r('hello');
echo '<br/>';
reverse_i('hello');
//phpinfo();