php include 和 require區別

剛接觸php不久，碰到include和require, 在網上查了很久，很多人也做了比較，有些不大正確，有誤導之嫌，最權威的正確的答案在這裡：http://cn.php.net/manual/zh/function.include.php。
看了如果還不明白的話，我做了以下測試，
情況一：
<?php
include("./est.php"); // est.php不存在
echo "<br>continue...";
?>

測試結果：
Warning: include(./est.php): failed to open stream: No such file or directory in .../test1.php on line 2 Warning: include(): Failed opening './est.php' for inclusion (include_path='.:/usr/local/Cellar/php/5.3.10/lib/php') in .../test1.php on line 2
continue...

情況二：
<?php
require("./est.php");
echo "<br>continue...";
?>

測試結果：
Warning: require(./est.php): failed to open stream: No such file or directory in .../test1.php on line 2 Fatal error: require(): Failed opening required './est.php' (include_path='.:/usr/local/Cellar/php/5.3.10/lib/php') in .../test1.php on line 2
此處continue字串沒有列印出來。

