本篇文章带大家深入理解PHP中的echo语句。有一定的参考价值，有需要的朋友可以参考一下，希望对大家有所帮助。
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本篇文章带大家深入理解PHP中的echo语句。有一定的参考价值，有需要的朋友可以参考一下，希望对大家有所帮助。
1、概述
2、官方文档(php.net)2.1 输出一个或多个字符串void echo ( string $arg1 [, string $... ] )
2.2 说明
2.3 注释
<?php /** * Tip * 相对 echo 中拼接字符串而言，传递多个参数比较好，考虑到了 PHP 中连接运算符（“.”）的优先级。 传入多个参数，不需要圆括号保证优先级： */ echo "Sum: ", 1 + 2; echo "Hello ", isset($name) ? $name : "John Doe", "!"; /** Tip * 如果是拼接的，相对于加号和三目元算符，连接运算符（“.”）具有更高优先级。为了正确性，必须使用圆括号： */ echo 'Sum: ' . (1 + 2); echo 'Hello ' . (isset($name) ? $name : 'John Doe') . '!'; 3、应用3.1 输出基本数据类型echo 123, 'abc', [12, 34]; // 123abcArray echo "Sum: ", 1 + 2; // Sum: 3 echo 'Sum: ' . (1 + 2); // Sum: 3 echo "Hello ", isset($name) ? $name : "John Doe", "!"; // Hello John Doe! echo 'Hello ' . (isset($name) ? $name : 'John Doe') . '!'; // Hello John Doe! 3.2 输出对象类型<?php
class Customer {
public function say() {
return 'Hello World';
}
}
echo (new Customer());
输出对象时汇报以上错误, 所以如果需要输出对象, 一定要在其内部实现 <?php
class Customer {
public function say() {
return 'Hello World';
}
/**
* __toString() 方法用于一个类被当成字符串时应怎样回应。例如 echo $obj; 应该显示些什么。此方法必须返回一个字符串，否则将发出一条 E_RECOVERABLE_ERROR 级别的致命错误。
*/
public function __toString(){
return $this->say();
}
}
echo (new Customer()); // Hello World3.3 输出资源类型echo tmpfile(); // Resource id #1 4、源码4.1 源码概述
对应的文件在 4.2 字符转标记(Zend/zend_language_scanner.l)<ST_IN_SCRIPTING>"echo" {
RETURN_TOKEN(T_ECHO);
}ZEND引擎在读取一个PHP文件之后会先进行词法分析，就是用lex扫描，把对应的PHP字符转换成相应的标记（也叫token)，比如 4.3 语法分析(Zend/zend_language_parser.y)# %token Token就是一个个的“词块”
%token T_ECHO "echo (T_ECHO)"
# statement T_ECHO echo_expr_list
statement:
'{' inner_statement_list '}' { ? = $2; }
| if_stmt { ? = $1; }
| alt_if_stmt { ? = $1; }
| T_WHILE '(' expr ')' while_statement
{ ? = zend_ast_create(ZEND_AST_WHILE, $3, $5); }
| T_DO statement T_WHILE '(' expr ')' ';'
{ ? = zend_ast_create(ZEND_AST_DO_WHILE, $2, $5); }
| T_FOR '(' for_exprs ';' for_exprs ';' for_exprs ')' for_statement
{ ? = zend_ast_create(ZEND_AST_FOR, $3, $5, $7, $9); }
| T_SWITCH '(' expr ')' switch_case_list
{ ? = zend_ast_create(ZEND_AST_SWITCH, $3, $5); }
| T_BREAK optional_expr ';' { ? = zend_ast_create(ZEND_AST_BREAK, $2); }
| T_CONTINUE optional_expr ';' { ? = zend_ast_create(ZEND_AST_CONTINUE, $2); }
| T_RETURN optional_expr ';' { ? = zend_ast_create(ZEND_AST_RETURN, $2); }
| T_GLOBAL global_var_list ';' { ? = $2; }
| T_STATIC static_var_list ';' { ? = $2; }
| T_ECHO echo_expr_list ';' { ? = $2; }
| T_INLINE_HTML { ? = zend_ast_create(ZEND_AST_ECHO, $1); }
| expr ';' { ? = $1; }
| T_UNSET '(' unset_variables ')' ';' { ? = $3; }
| T_FOREACH '(' expr T_AS foreach_variable ')' foreach_statement
{ ? = zend_ast_create(ZEND_AST_FOREACH, $3, $5, NULL, $7); }
| T_FOREACH '(' expr T_AS foreach_variable T_DOUBLE_ARROW foreach_variable ')'
foreach_statement
{ ? = zend_ast_create(ZEND_AST_FOREACH, $3, $7, $5, $9); }
| T_DECLARE '(' const_list ')'
{ zend_handle_encoding_declaration($3); }
declare_statement
{ ? = zend_ast_create(ZEND_AST_DECLARE, $3, $6); }
| ';' /* empty statement */ { ? = NULL; }
| T_TRY '{' inner_statement_list '}' catch_list finally_statement
{ ? = zend_ast_create(ZEND_AST_TRY, $3, $5, $6); }
| T_THROW expr ';' { ? = zend_ast_create(ZEND_AST_THROW, $2); }
| T_GOTO T_STRING ';' { ? = zend_ast_create(ZEND_AST_GOTO, $2); }
| T_STRING ':' { ? = zend_ast_create(ZEND_AST_LABEL, $1); }
;在 # echo_expr_list
echo_expr_list:
echo_expr_list ',' echo_expr { ? = zend_ast_list_add($1, $3); }
| echo_expr { ? = zend_ast_create_list(1, ZEND_AST_STMT_LIST, $1); }
;
echo_expr:
expr { ? = zend_ast_create(ZEND_AST_ECHO, $1); }
;
expr:
variable { ? = $1; }
| expr_without_variable { ? = $1; }
;词法分析后得到单独存在的词块不能表达完整的语义，还需要借助规则进行组织串联。语法分析器就是这个组织者。它会检查语法、匹配Token，对Token进行关联。PHP7中，组织串联的产物就是抽象语法树（ 这么看比较难理解，接下来我们从一个简单的例子看下最终生成的语法树。 $a = 123; $b = "hi~"; echo $a,$b; 具体解析过程这里不再解释，有兴趣的可以翻下zend_language_parse.y中，这个过程不太容易理解，需要多领悟几遍，最后生成的ast如下图：
4.4 模块初始化(main/main.c)通过 # php_module_startup zend_utility_functions zuf; // ... gc_globals_ctor(); zuf.error_function = php_error_cb; zuf.printf_function = php_printf; zuf.write_function = php_output_wrapper; zuf.fopen_function = php_fopen_wrapper_for_zend; zuf.message_handler = php_message_handler_for_zend; zuf.get_configuration_directive = php_get_configuration_directive_for_zend; zuf.ticks_function = php_run_ticks; zuf.on_timeout = php_on_timeout; zuf.stream_open_function = php_stream_open_for_zend; zuf.printf_to_smart_string_function = php_printf_to_smart_string; zuf.printf_to_smart_str_function = php_printf_to_smart_str; zuf.getenv_function = sapi_getenv; zuf.resolve_path_function = php_resolve_path_for_zend; zend_startup(&zuf, NULL);
/* {{{ php_output_wrapper
*/
static size_t php_output_wrapper(const char *str, size_t str_length)
{
return php_output_write(str, str_length);
}在 /* {{{ int php_output_write(const char *str, size_t len)
* Buffered write
* #define PHP_OUTPUT_ACTIVATED 0x100000
* 当flags=PHP_OUTPUT_ACTIVATED，会调用sapi_module.ub_write输出, 每个SAPI都有自已的实现, cli中是调用sapi_cli_single_write()
* php_output_write(); //输出，有buffer, 调用php_output_op()
* php_output_write_unbuffered();//输出，没有buffer，调用PHP_OUTPUT_ACTIVATED，会调用sapi_module.ub_write
* php_output_set_status(); //用于SAPI设置output.flags
* php_output_get_status(); //获取output.flags的值
*/
PHPAPI size_t php_output_write(const char *str, size_t len)
{
if (OG(flags) & PHP_OUTPUT_ACTIVATED) {
php_output_op(PHP_OUTPUT_HANDLER_WRITE, str, len);
return len;
}
if (OG(flags) & PHP_OUTPUT_DISABLED) {
return 0;
}
return php_output_direct(str, len);
}
/* }}} */4.5 输出的终点(main/output.c fwrite函数)不调用sapi_module的输出 static size_t (*php_output_direct)(const char *str, size_t str_len) = php_output_stderr;
static size_t php_output_stderr(const char *str, size_t str_len)
{
fwrite(str, 1, str_len, stderr);
/* See http://support.microsoft.com/kb/190351 */
#ifdef PHP_WIN32
fflush(stderr);
#endif
return str_len;
}调用sapi_module的输出 sapi_module.ub_write(context.out.data, context.out.used);
if (OG(flags) & PHP_OUTPUT_IMPLICITFLUSH) {
sapi_flush();
}
/* {{{ static void php_output_op(int op, const char *str, size_t len)
* Output op dispatcher, passes input and output handlers output through the output handler stack until it gets written to the SAPI
*/
static inline void php_output_op(int op, const char *str, size_t len)
{
php_output_context context;
php_output_handler **active;
int obh_cnt;
if (php_output_lock_error(op)) {
return;
}
php_output_context_init(&context, op);
/*
* broken up for better performance:
* - apply op to the one active handler; note that OG(active) might be popped off the stack on a flush
* - or apply op to the handler stack
*/
if (OG(active) && (obh_cnt = zend_stack_count(&OG(handlers)))) {
context.in.data = (char *) str;
context.in.used = len;
if (obh_cnt > 1) {
zend_stack_apply_with_argument(&OG(handlers), ZEND_STACK_APPLY_TOPDOWN, php_output_stack_apply_op, &context);
} else if ((active = zend_stack_top(&OG(handlers))) && (!((*active)->flags & PHP_OUTPUT_HANDLER_DISABLED))) {
php_output_handler_op(*active, &context);
} else {
php_output_context_pass(&context);
}
} else {
context.out.data = (char *) str;
context.out.used = len;
}
if (context.out.data && context.out.used) {
php_output_header();
if (!(OG(flags) & PHP_OUTPUT_DISABLED)) {
#if PHP_OUTPUT_DEBUG
fprintf(stderr, "::: sapi_write('%s', %zu)\n", context.out.data, context.out.used);
#endif
sapi_module.ub_write(context.out.data, context.out.used);
if (OG(flags) & PHP_OUTPUT_IMPLICITFLUSH) {
sapi_flush();
}
OG(flags) |= PHP_OUTPUT_SENT;
}
}
php_output_context_dtor(&context);
}以上了解了PHP输出函数的实现, 接下来了解echo实现. 4.6 输出动作的ZEND引擎实现(Zend/zend_vm_def.h)ZEND_VM_HANDLER(40, ZEND_ECHO, CONST|TMPVAR|CV, ANY)
{
USE_OPLINE
zend_free_op free_op1;
zval *z;
SAVE_OPLINE();
z = GET_OP1_ZVAL_PTR_UNDEF(BP_VAR_R);
if (Z_TYPE_P(z) == IS_STRING) {
zend_string *str = Z_STR_P(z);
if (ZSTR_LEN(str) != 0) {
zend_write(ZSTR_VAL(str), ZSTR_LEN(str));
}
} else {
zend_string *str = _zval_get_string_func(z);
if (ZSTR_LEN(str) != 0) {
zend_write(ZSTR_VAL(str), ZSTR_LEN(str));
} else if (OP1_TYPE == IS_CV && UNEXPECTED(Z_TYPE_P(z) == IS_UNDEF)) {
GET_OP1_UNDEF_CV(z, BP_VAR_R);
}
zend_string_release(str);
}
FREE_OP1();
ZEND_VM_NEXT_OPCODE_CHECK_EXCEPTION();
}可以看到在 4.7 zend_write实现(Zend/zend.c)# Zend/zend.h typedef int (*zend_write_func_t)(const char *str, size_t str_length); # Zend/zend.c ZEND_API zend_write_func_t zend_write; # 如下图所示, zend_write的初始化是在zend_startup()函数里面，这是zend引擎启动的时候需要做的一些初始化工作，有下面一句： zend_write = (zend_write_func_t) utility_functions->write_function; // php_output_wrapper
zuf.write_function = php_output_wrapper;
5、php(echo)加速5.1 PHP echo 真的慢么?
但是在某些时候 那么使用 5.2 还是可以优化的: 打开输出缓存
# 编辑php.ini output_buffering = 4096 //bytes # 调用ob_start() ob_start(); echo $hugeString; ob_end_flush();
6、输出时的类型转换6.1 输出时的类型转换规则
6.2 输出时的类型转换源码(Zend/zend_operators.h & Zend/zend_operators.c)# Zend/zend_operators.h
ZEND_API zend_string* ZEND_FASTCALL _zval_get_string_func(zval *op);
# Zend/zend_operators.c
ZEND_API zend_string* ZEND_FASTCALL _zval_get_string_func(zval *op) /* {{{ */
{
try_again:
switch (Z_TYPE_P(op)) {
case IS_UNDEF:
case IS_NULL:
case IS_FALSE:
return ZSTR_EMPTY_ALLOC();
case IS_TRUE:
if (CG(one_char_string)['1']) {
return CG(one_char_string)['1'];
} else {
return zend_string_init("1", 1, 0);
}
case IS_RESOURCE: {
char buf[sizeof("Resource id #") + MAX_LENGTH_OF_LONG];
int len;
len = snprintf(buf, sizeof(buf), "Resource id #" ZEND_LONG_FMT, (zend_long)Z_RES_HANDLE_P(op));
return zend_string_init(buf, len, 0);
}
case IS_LONG: {
return zend_long_to_str(Z_LVAL_P(op));
}
case IS_DOUBLE: {
return zend_strpprintf(0, "%.*G", (int) EG(precision), Z_DVAL_P(op));
}
case IS_ARRAY:
zend_error(E_NOTICE, "Array to string conversion");
return zend_string_init("Array", sizeof("Array")-1, 0);
case IS_OBJECT: {
zval tmp;
if (Z_OBJ_HT_P(op)->cast_object) {
if (Z_OBJ_HT_P(op)->cast_object(op, &tmp, IS_STRING) == SUCCESS) {
return Z_STR(tmp);
}
} else if (Z_OBJ_HT_P(op)->get) {
zval *z = Z_OBJ_HT_P(op)->get(op, &tmp);
if (Z_TYPE_P(z) != IS_OBJECT) {
zend_string *str = zval_get_string(z);
zval_ptr_dtor(z);
return str;
}
zval_ptr_dtor(z);
}
zend_error(EG(exception) ? E_ERROR : E_RECOVERABLE_ERROR, "Object of class %s could not be converted to string", ZSTR_VAL(Z_OBJCE_P(op)->name));
return ZSTR_EMPTY_ALLOC();
}
case IS_REFERENCE:
op = Z_REFVAL_P(op);
goto try_again;
case IS_STRING:
return zend_string_copy(Z_STR_P(op));
EMPTY_SWITCH_DEFAULT_CASE()
}
return NULL;
}
/* }}} */7、Zend/zend_compile.c对echo的解析7.1 源码地址
7.2 |
