深入理解PHP之require/include顺序 [url=http://www.1sucai.cn/article/25867.htm]http://www.1sucai.cn/article/25867.htm[/url] [b]普及[/b] 在php手册中： [quote] 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. [/quote] 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？） [img]http://files.jb51.net/upload/201101/20110102134908104.jpg[/img] [quote] 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 [/quote] [b]正题[/b] 下面看操作记录： [quote] 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。 [/quote] 开始深入： [quote] 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 } [/quote] 然后再搜一下T_REQUIRE_ONCE, [quote] 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); } [/quote] 在985行附近，有这样一群代码： [quote] 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, &$$, &$2 TSRMLS_CC); } ; [/quote] 于是乎，我们需要继续深入寻找zend_do_include_or_eval， [quote] cc@cc-laptop:/opt/workspace/php-src-5.3$ 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) /* {{{ */ [/quote] 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： [quote] 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} [/quote] 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： [quote] //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 [/quote] [b]总结[/b] 和开头PHP手册所说完全一致，require和include的区别在于，出现错误时，一个是error一个是warning。