Php-echo principle

1. Grammatical analysis

unticked_statement:| T_echo echo_expr_list';'; Echo_expr_list:echo_expr_list','Expr {Zend_do_echo (&$3tsrmls_cc); }    | Expr {Zend_do_echo (&$1tsrmls_cc); };expr:r_variable {$$= $1; } | expr_without_variable {$$ = $1; }; r_variable:variable {zend_do_end_variable_parse (&$1, Bp_var_r,0TSRMLS_CC); $$ = $1; }; Variable:| base_variable_with_function_calls {$$ = $1; }; base_variable_with_function_calls:base_variable {$$= $1; } ; Reference_variable:| compound_variable {zend_do_begin_variable_parse (Tsrmls_c); Fetch_simple_variable (&$$, &$1,1tsrmls_cc); };compound_variable:t_variable {$$= $1; } |'$' '{'Expr'}'{ $$ = $3; };

2. Compile Build opcode

void Zend_do_echo (const/**/{    *opline = Get_next_op ( CG (Active_op_array) tsrmls_cc);    Opline->opcode = Zend_echo;    Set_node (opline-OP1, ARG);    Set_unused (Opline-op2);}

3. Execute the opcode that have been generated

Static int Zend_fastcall  Zend_echo_spec_cv_handler (Zend_opcode_handler_args) {    use_opline    *z;    Save_opline ();     = _get_zval_ptr_cv_bp_var_r (Ex_cvs (), Opline->op1.  var  tsrmls_cc); //This z is already a    value.  if (IS_CV = = Is_tmp_var && z_type_p (z) = = is_object) {        init_pzval (z);    }    Zend_print_variable (z);    Check_exception ();    Zend_vm_next_opcode ();}

StaticZend_always_inline zval *_get_zval_ptr_cv_bp_var_r (zval ***cvs, Zend_uintvartsrmls_dc) {Zvalptr = &CV (var); //eg (Active_op_array). Vars[key] The result is a zend_compile_variable, where key is the variable var of znod_op, which is a number that can be understood as the first variable, and finally in the EG (active_ sysbole_table), and put the data in Ex (CVS) [key] if(Unexpected (*ptr = =NULL)) {        return*_get_zval_cv_lookup_bp_var_r (PTR,vartsrmls_cc); }    return**ptr;}StaticZend_never_inline zval **_get_zval_cv_lookup_bp_var_r (zval ***ptr, Zend_uintvartsrmls_dc) {zend_compiled_variable*CV = &cv_def_of (var); if(! EG (active_symbol_table) | |Zend_hash_quick_find (EG (active_symbol_table), CV->name, cv->name_len+1, Cv->hash_value, (void* *) ptr) = =FAILURE) {Zend_error (E_notice,"Undefined variable:%s", cv->name); return&EG (UNINITIALIZED_ZVAL_PTR); }    return*ptr;}

Zend_apiintZend_print_variable (Zval *var) {    returnZend_print_zval (var,0);} Zend_apiintZend_print_zval (Zval *expr,intIndent/* {{{ */{    returnzend_print_zval_ex (zend_write, expr, indent);} Zend_apiintZEND_PRINT_ZVAL_EX (zend_write_func_t write_func, Zval *expr,intIndent/* {{{ */{zval expr_copy; intuse_copy; Zend_make_printable_zval (expr,&expr_copy, &use_copy); if(use_copy) {expr= &expr_copy; }    if(Z_strlen_p (expr) = =0) {/*optimize away empty strings*/        if(use_copy) {zval_dtor (expr); }        return 0;    } write_func (Z_strval_p (expr), z_strlen_p (expr)); if(use_copy) {zval_dtor (expr); }    returnz_strlen_p (expr);}intPhp_module_startup (sapi_module_struct *sf, Zend_module_entry *additional_modules,UINTnum_additional_modules)    {zend_utility_functions Zuf;    Zend_utility_values Zuv; intretval = SUCCESS, module_number=0;/*For register_ini_entries ()*/.........  Sapi_module= *SF;    Php_output_startup (); 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.block_interruptions=sapi_module.block_interruptions; Zuf.unblock_interruptions=sapi_module.unblock_interruptions; 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.vspprintf_function=vspprintf; Zuf.getenv_function=sapi_getenv; Zuf.resolve_path_function=Php_resolve_path_for_zend; Zend_startup (&zuf, NULL tsrmls_cc);

Static intPhp_output_wrapper (Const Char*STR,UINTstr_length)    {Tsrmls_fetch (); returnphp_output_write (str, str_length tsrmls_cc);} PhpapiintPhp_output_write (Const Char*str, size_t len TSRMLS_DC) {    if(OG (Flags) &php_output_disabled) {        return 0; }    if(OG (Flags) &php_output_activated)        {php_output_op (php_output_handler_write, str, Len TSRMLS_CC); return(int) Len; }    returnphp_output_direct (str, len);}Static int(*php_output_direct) (Const Char*str, size_t str_len) =Php_output_stderr;Static intPhp_output_stderr (Const Char*str, size_t Str_len) { fwrite (str, 1, Str_len, stderr); You know that echo is output with fwrite./* Seehttp://support.microsoft.com/kb/190351 */#ifdef php_win32 fflush (stderr);#endif    returnStr_len;}

Reference: http://wenku.baidu.com/view/b7d2d4335a8102d276a22fb1.html

Php-echo principle