./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
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。
