切忌使用复制粘贴
您可以从其他地方将代码复制粘贴到自己的代码编辑器，但这样做有利也有弊。好的一面是，从一个示例或模板中复制代码能够避免很多错误。不好的一面是，这容易带来大量的类似编程方式。
一定要注意，不要将代码从应用程序的一部分复制粘贴到另一部分。如果您采用这种方式，请停止这个不良的习惯，然后考虑将这段代码重写为可重用的。一般而言，将代码放置到一个地方便于日后的维护，因为这样只需在一个地方更改代码。
不良习惯：类似的代码段
清单 9 给出了几个几乎一样的方法，只是其中的值不同而已。有一些工具可以帮助找到复制粘贴过来的代码(参见 参考资料)。
清单 9. 不良习惯：类似的代码段
<?php
/**
* Counts the number of messages found in the array of
* ResultMessage with the getSeverity() value of "Error"
*
* @param $messages An array of ResultMessage
* @return unknown_type
*/
function countErrors($messages)
{
$matchingCount = 0;
foreach($messages as $m) {
if ($m->getSeverity() == "Error") {
$matchingCount++;
}
}
return $matchingCount;
}
/**
* Counts the number of messages found in the array of
* ResultMessage with the getSeverity() value of "Warning"
*
* @param $messages An array of ResultMessage
* @return unknown_type
*/
function countWarnings($messages)
{
$matchingCount = 0;
foreach($messages as $m) {
if ($m->getSeverity() == "Warning") {
$matchingCount++;
}
}
return $matchingCount;
}
/**
* Counts the number of messages found in the array of
* ResultMessage with the getSeverity() value of "Information"
*
* @param $messages An array of ResultMessage
* @return unknown_type
*/
function countInformation($messages)
{
$matchingCount = 0;
foreach($messages as $m) {
if ($m->getSeverity() == "Information") {
$matchingCount++;
}
}
return $matchingCount;
}
$messages = array(new ResultMessage("Error", "This is an error!"),
new ResultMessage("Warning", "This is a warning!"),
new ResultMessage("Error", "This is another error!"));
$errs = countErrors($messages);
echo("There are " . $errs . " errors in the result.\n");
?>
/**
* Counts the number of messages found in the array of
* ResultMessage with the getSeverity() value of "Error"
*
* @param $messages An array of ResultMessage
* @return unknown_type
*/
function countErrors($messages)
{
$matchingCount = 0;
foreach($messages as $m) {
if ($m->getSeverity() == "Error") {
$matchingCount++;
}
}
return $matchingCount;
}
/**
* Counts the number of messages found in the array of
* ResultMessage with the getSeverity() value of "Warning"
*
* @param $messages An array of ResultMessage
* @return unknown_type
*/
function countWarnings($messages)
{
$matchingCount = 0;
foreach($messages as $m) {
if ($m->getSeverity() == "Warning") {
$matchingCount++;
}
}
return $matchingCount;
}
/**
* Counts the number of messages found in the array of
* ResultMessage with the getSeverity() value of "Information"
*
* @param $messages An array of ResultMessage
* @return unknown_type
*/
function countInformation($messages)
{
$matchingCount = 0;
foreach($messages as $m) {
if ($m->getSeverity() == "Information") {
$matchingCount++;
}
}
return $matchingCount;
}
$messages = array(new ResultMessage("Error", "This is an error!"),
new ResultMessage("Warning", "This is a warning!"),
new ResultMessage("Error", "This is another error!"));
$errs = countErrors($messages);
echo("There are " . $errs . " errors in the result.\n");
?>
良好习惯：带参数的可重用函数
清单 10 展示了修改后的代码，它将复制的代码放到一个方法中。另一个方法也进行了更改，它现在将任务委托给新的方法。构建通用的方法需要花时间设计，并且这样做使您能停下来思考，而不是本能地使用复制粘贴。但有必要进行更改时，对通用的方法投入的时间将得到回报。
清单 10. 良好习惯：带参数的可重用函数
<?php
/*
* Counts the messages with the given severity in the array
* of messages.
*
* @param $messages An array of ResultMessage
* @return int Count of messages matching $withSeverity
*/
function countMessages($messages, $withSeverity)
{
$matchingCount = 0;
foreach($messages as $m) {
if ($m->getSeverity() == $withSeverity) {
$matchingCount++;
}
}
return $matchingCount;
}
/**
* Counts the number of messages found in the array of
* ResultMessage with the getSeverity() value of "Error"
*
* @param $messages An array of ResultMessage
* @return unknown_type
*/
function countErrors($messages)
{
return countMessages($messages, "Errors");
}
/**
* Counts the number of messages found in the array of
* ResultMessage with the getSeverity() value of "Warning"
*
* @param $messages An array of ResultMessage
* @return unknown_type
*/
function countWarnings($messages)
{
return countMessages($messages, "Warning");
}
/**
* Counts the number of messages found in the array of
* ResultMessage with the getSeverity() value of "Warning"
*
* @param $messages An array of ResultMessage
* @return unknown_type
*/
function countInformation($messages)
{
return countMessages($messages, "Information");
}
$messages = array(new ResultMessage("Error", "This is an error!"),
new ResultMessage("Warning", "This is a warning!"),
new ResultMessage("Error", "This is another error!"));
$errs = countErrors($messages);
echo("There are " . $errs . " errors in the result.\n");
?>
/*
* Counts the messages with the given severity in the array
* of messages.
*
* @param $messages An array of ResultMessage
* @return int Count of messages matching $withSeverity
*/
function countMessages($messages, $withSeverity)
{
$matchingCount = 0;
foreach($messages as $m) {
if ($m->getSeverity() == $withSeverity) {
$matchingCount++;
}
}
return $matchingCount;
}
/**
* Counts the number of messages found in the array of
* ResultMessage with the getSeverity() value of "Error"
*
* @param $messages An array of ResultMessage
* @return unknown_type
*/
function countErrors($messages)
{
return countMessages($messages, "Errors");
}
/**
* Counts the number of messages found in the array of
* ResultMessage with the getSeverity() value of "Warning"
*
* @param $messages An array of ResultMessage
* @return unknown_type
*/
function countWarnings($messages)
{
return countMessages($messages, "Warning");
}
/**
* Counts the number of messages found in the array of
* ResultMessage with the getSeverity() value of "Warning"
*
* @param $messages An array of ResultMessage
* @return unknown_type
*/
function countInformation($messages)
{
return countMessages($messages, "Information");
}
$messages = array(new ResultMessage("Error", "This is an error!"),
new ResultMessage("Warning", "This is a warning!"),
new ResultMessage("Error", "This is another error!"));
$errs = countErrors($messages);
echo("There are " . $errs . " errors in the result.\n");
?>
