PHP中feof()函数实例测试_php技巧
本文实例讲述了PHP中的feof()函数的用法，针对feof()函数进行了一定的测试，很有实用价值。具体分析如下：
本文实例运行环境：
OS：Mac OS X 10.8.4
PHP：5.3.15
在PHP的官方手册中，函数feof()下面的讨论不少，对此做了一些相关的测试如下。
测试代码如下：
<?php
print <<<EOF
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>测试PHP中的feof()函数效果</title>
</head>
<body>
<div>
EOF;
function bool2str($bool) {
if ($bool == TRUE) {
return "TRUE";
} else {
return "FALSE";
}
}
/*
* 请随便创建一个文件。
* 比如：本测试中，在脚本文件的相同路径下创建了一个文本文件，
* 文件内容为“abcdefg”，文件名为“7bytesfile”。
*/
$filename = './7bytesfile';
$handle = fopen($filename, 'r');
if (!$handle) {
die("文件打开失败");
}
for($i = 0; $i <= filesize($filename); $i++) {
fseek($handle, $i);
echo "文件位置" . ftell($handle) . "：<br />\n";
echo "执行fseek，尚未执行读取操作之前，feof结果：" . bool2str(feof($handle)) . "<br />\n";
echo "当前位置字符：" . fgetc($handle) . "<br />\n";
echo "执行文件读取操作之后，feof结果：" . bool2str(feof($handle)) . "<hr />\n";
}
/*
* 通过上面一段代码可以观察到，
* 随着循环的执行，文件指针从文件头一直移动到文件末尾。
* 但是当完成了字符“g”的读取输出，文件指针继续向后移动，这是feof()依然返回False。
* 只有当执行了一次fgetc()操作之后，才返回true，表示到达文件末尾。
*/
echo "ftell()结果：". ftell($handle). "<hr />\n";
//输出一下，很郁闷的发现文件指针的位置还是7。+_+
fseek($handle, 4);
echo "文件位置" . ftell($handle) . "：<br />\n";
echo "执行fseek，尚未执行读取操作之前，feof结果：" . bool2str(feof($handle)) . "<br />\n";
echo "当前位置字符：" . fgetc($handle) . "<br />\n";
echo "执行文件读取操作之后，feof结果：" . bool2str(feof($handle)) . "<hr />\n";
fseek($handle, 7);
echo "文件位置" . ftell($handle) . "：<br />\n";
echo "执行fseek，尚未执行读取操作之前，feof结果：" . bool2str(feof($handle)) . "<br />\n";
echo "当前位置字符：" . fgetc($handle) . "<br />\n";
echo "执行文件读取操作之后，feof结果：" . bool2str(feof($handle)) . "<hr />\n";
fclose($handle);
//再次移动文件指针，效果依旧。
//再用另外一段代码测试一下：
$handle = fopen($filename, 'r');
if (!$handle) {
die("文件打开失败");
}
while (!feof($handle)) {
$char = fgetc($handle);
if ($char === FALSE) {
echo 'FALSE';
} else {
echo $char;
}
}
fclose($handle);
//依然是输出了字符g之后，再次执行读取操作，才终止循环。
print <<<EOF
</div>
</body>
</html>
EOF;
?>
针对这种情况的猜测是，在PHP中，feof()的实现方式并非直接检查文件指针相对于文件的位置，而是根据某个标识返回结果。每次fseek()之后都会都会把这个标识设置为“False”，只有当执行一次文件内容读取操作之后，才会根据文件读取的结果对标识进行设置。
根据这种猜测，可以使用两种代码逻辑。
一个方法是不做feof()检测，直接检测内容读取函数（比如fgetc()、fgets()）的执行结果。
示例代码如下：
while (($content = fgets($fileHandle)) !==FALSE) {
//文件内容处理……
}
这种处理办法，利用了PHP被诟病的函数返回方式，所以得用“===”或“!==”进行检测，不能把代码简化成：
while ($content = fgets($fileHandle)) {}
另外一个方法是先进行一次文件读取，然后再进入feof()循环，如下所示：
$content = fgets($fileHandle);
while (!feof($fileHandle)) {
//处理文件内容……
$content = fgets($fileHandle);
}
经过测试，前一种方法效率会高一些。
希望本文示例对大家PHP程序设计有所帮助。
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