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先編輯command.php文件

echo 'hello'.PHP_EOL;

然后編輯console.php文件

for($i=1;$i<=3;++$i){
	require 'command1.php';
}

原本想要包含并執(zhí)行這個echo，沒想到寫錯了文件名，如果是require，會報出這樣的錯誤：

Warning: require(command1.php): failed to open stream: No such file or directory in console.php on line 4

Fatal error: require(): Failed opening required 'command1.php' (include_path='.') in console.php on line 4
PHP Warning: require(command1.php): failed to open stream: No such file or directory in console.php on line 4
PHP Fatal error: require(): Failed opening required 'command1.php' (include_path='.') in console.php on line 4

如果把require改為include

for($i=1;$i<=3;++$i){
	include 'command1.php';
}

會報出這樣的錯誤：

Warning: include(command1.php): failed to open stream: No such file or directory in console.php on line 4

Warning: include(): Failed opening 'command1.php' for inclusion (include_path='.') in console.php on line 4

Warning: include(command1.php): failed to open stream: No such file or directory in console.php on line 4

Warning: include(): Failed opening 'command1.php' for inclusion (include_path='.') in console.php on line 4

Warning: include(command1.php): failed to open stream: No such file or directory in console.php on line 4

Warning: include(): Failed opening 'command1.php' for inclusion (include_path='.') in console.php on line 4
PHP Warning: include(command1.php): failed to open stream: No such file or directory in console.php on line 4
PHP Warning: include(): Failed opening 'command1.php' for inclusion (include_path='.') in console.php on line 4
PHP Warning: include(command1.php): failed to open stream: No such file or directory in console.php on line 4
PHP Warning: include(): Failed opening 'command1.php' for inclusion (include_path='.') in console.php on line 4
PHP Warning: include(command1.php): failed to open stream: No such file or directory in console.php on line 4
PHP Warning: include(): Failed opening 'command1.php' for inclusion (include_path='.') in console.php on line 4

如果使用require_once或者include_once，只要包含路徑正確，那么循環(huán)只執(zhí)行一次。

總結(jié)：

使用require，如果文件沒有包含成功，就會報出一個fatal error，整個程序就中止了。

使用include，如果文件沒有包含成功，就會報出一個普通的warning，之后的代碼仍會執(zhí)行。

如果你的Web程序使用了MVC這種對文件包含強依賴的設計方法，請使用require_once。