深入理解PHP之require/include顺序 //www.jb51.cc/article/25867.htm

普及

require() is identical to include() except upon failure it will also produce a fatal E_ERROR level error. In other words,it will halt the script whereas include() only emits a warning (E_WARNING) which allows the script to continue.

就是说在失败的时候，require是会中止PHP运行的，而include是可以继续运行的。
倒底有什么样的区别呢？我们带着这个疑问来一起进入PHP的核心代码。
下面是一个PHP运行过程的图（这个图是出自哪里的？鸟哥画的？）
PHP " src="http:https://files.jb51.cc/upload/201101/20110102134908104.jpg">

补习一下：lex是代码扫描器，扫描代码用的，yacc是Yet Another Compiler Compiler，作用是把任何一种代码的语法转成yacc语法，yacc就是解析器（真TMD绕）。
lex在c下的后缀是*.l yacc是*.y

正题

cc@cc-laptop:/opt/workspace$ svn checkout http://svn.PHP.net/repository/PHP/PHP-src/branches/PHP_5_3 PHP-src-5.3
从svn取最新的PHP源代码。

开始深入：

cc@cc-laptop:/opt/workspace/PHP-src-5.3$ find . -type f -name “*.l” -exec grep -Hn “require_once” {} \;
./Zend/zend_language_scanner.l:1093:”require_once” {
寻找lex代码扫描器文件中出现require_once的地方，zend_language_scanner.l的1093行。
1093 “require_once” {
1094 return T_REQUIRE_ONCE;
1095 }

然后再搜一下T_REQUIRE_ONCE,

cc@cc-laptop:/opt/workspace/PHP-src-5.3$ find . -type f -name “*.y” -exec grep -Hn “T_INCLUDE” {} \;
./Zend/zend_language_parser.y:52:%left T_INCLUDE T_INCLUDE_ONCE T_EVAL T_REQUIRE T_REQUIRE_ONCE
./Zend/zend_language_parser.y:985: | T_INCLUDE expr { zend_do_include_or_eval(ZEND_INCLUDE,&$$,&$2 TSRMLS_CC); }
./Zend/zend_language_parser.y:986: | T_INCLUDE_ONCE expr { zend_do_include_or_eval(ZEND_INCLUDE_ONCE,&$2 TSRMLS_CC); }

在985行附近，有这样一群代码：

internal_functions_in_yacc:
T_ISSET ‘(‘ isset_variables ‘)' { $$ = $3; }
| T_EMPTY ‘(‘ variable ‘)' { zend_do_isset_or_isempty(ZEND_ISEMPTY,&$3 TSRMLS_CC); }
| T_INCLUDE expr { zend_do_include_or_eval(ZEND_INCLUDE,&$2 TSRMLS_CC); }
| T_INCLUDE_ONCE expr { zend_do_include_or_eval(ZEND_INCLUDE_ONCE,&$2 TSRMLS_CC); }
| T_EVAL ‘(‘ expr ‘)' { zend_do_include_or_eval(ZEND_EVAL,&$3 TSRMLS_CC); }
| T_REQUIRE expr { zend_do_include_or_eval(ZEND_REQUIRE,&$2 TSRMLS_CC); }
| T_REQUIRE_ONCE expr { zend_do_include_or_eval(ZEND_REQUIRE_ONCE,&$2 TSRMLS_CC); }
;

于是乎，我们需要继续深入寻找zend_do_include_or_eval，

cc@cc-laptop:/opt/workspace/PHP-src-5.3$ find . -type f -name “*.c” -exec grep -Hn “zend_do_include_or_eval” {} \;
./Zend/zend_compile.c:4317:void zend_do_include_or_eval(int type,znode *result,const znode *op1 TSRMLS_DC) /* {{{ */

zend_do_include_or_eval中组装了一个结构体，ZEND_INCLUDE_OR_EVAL。

再在zend_vm_def.h中找到ZEND_VM_HANDLER(73,ZEND_INCLUDE_OR_EVAL,CONST|TMP|VAR|CV,ANY)：
switch (Z_LVAL(opline->op2.u.constant)) {代码略}

中间关键的一句是：
new_op_array = compile_filename(Z_LVAL(opline->op2.u.constant),inc_filename TSRMLS_CC);

在zend_complie.h文件中:
ZEND_API zend_op_array *compile_filename(int type,zval *filename TSRMLS_DC);

这个函数定义在zend_language_scaner.l文件中，找出最核心的代码：

if (open_file_for_scanning(file_handle TSRMLS_CC)==FAILURE) {
// require与include的差别：错误信息的显示级别（有bailout和无bailout）
if (type==ZEND_REQUIRE) { //require时
zend_message_dispatcher(ZMSG_Failed_REQUIRE_FOPEN,file_handle->filename TSRMLS_CC);
zend_bailout();
} else {
zend_message_dispatcher(ZMSG_Failed_INCLUDE_FOPEN,file_handle->filename TSRMLS_CC);
}
compilation_successful=0;
} else {代码略}

继续追踪zend_message_dispatcher可以在main/main.c文件中找到PHP_message_handler_for_zend函数：

//include输出错误信息时的级别为：E_WARNING
case ZMSG_Failed_INCLUDE_FOPEN:
PHP_error_docref(“function.include” TSRMLS_CC,E_WARNING,“Failed opening ‘%s' for inclusion (include_path='%s')”,PHP_strip_url_passwd((char *) data),STR_PRINT(PG(include_path)));
break;
//require输出错误信息时的级别为：E_COMPILE_ERROR
代码略

总结