In-depth understanding of php variable structure
This article mainly introduces the relevant knowledge of PHP variable structure. The article mentions zval in PHP5 and zval in PHP 7. The code is simple and easy to understand. Friends in need can refer to it
zval in PHP5
// 1. zval typedef struct _zval_struct { zvalue_value value; zend_uint refcount__gc; zend_uchar type; zend_uchar is_ref__gc; } zval; // 2. zvalue_value typedef union _zvalue_value { long lval; // 用于 bool 类型、整型和资源类型 double dval; // 用于浮点类型 struct { // 用于字符串 char *val; int len; } str; HashTable *ht; // 用于数组 zend_object_value obj; // 用于对象 zend_ast *ast; // 用于常量表达式(PHP5.6 才有) } zvalue_value; // 3. zend_object_value typedef struct _zend_object_value { zend_object_handle handle; const zend_object_handlers *handlers; } zend_object_value; // 4. zend_object_handle typedef unsigned int zend_object_handle;
Most articles, when mentioning the PHP5 variable structure, mention: sizeof(zval ) == 24, sizeof(zvalue_value) == 16. In fact, this statement is not accurate. When the CPU is 64bit, this result is correct.
But when the CPU is 32bit: sizeof(zval) == 16, sizeof(zvalue_value) == 8, mainly because when the CPU is 64bit, the pointer occupies 8 bytes, and when 32bit, the pointer is 4 bytes.
zval in PHP 7
##
// 1. zval struct _zval_struct { zend_value value; /* value */ union { struct { ZEND_ENDIAN_LOHI_4( zend_uchar type, /* active type */ zend_uchar type_flags, zend_uchar const_flags, zend_uchar reserved) /* call info for EX(This) */ } v; uint32_t type_info; } u1; union { uint32_t next; /* hash collision chain */ uint32_t cache_slot; /* literal cache slot */ uint32_t lineno; /* line number (for ast nodes) */ uint32_t num_args; /* arguments number for EX(This) */ uint32_t fe_pos; /* foreach position */ uint32_t fe_iter_idx; /* foreach iterator index */ uint32_t access_flags; /* class constant access flags */ uint32_t property_guard; /* single property guard */ } u2; }; // 2. zend_value typedef union _zend_value { zend_long lval; /* long value */ double dval; /* double value */ zend_refcounted *counted; zend_string *str; zend_array *arr; zend_object *obj; zend_resource *res; zend_reference *ref; zend_ast_ref *ast; zval *zv; void *ptr; zend_class_entry *ce; zend_function *func; struct { uint32_t w1; uint32_t w2; } ww; } zend_value;
Mainly look at the ww in zend_value, which is two uint32_t. This is always 8 bytes, so sizeof(zend_value) == 8, so sizeof(zval) == 16.
Summarize
The above is the detailed content of In-depth understanding of php variable structure. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics











JWT is an open standard based on JSON, used to securely transmit information between parties, mainly for identity authentication and information exchange. 1. JWT consists of three parts: Header, Payload and Signature. 2. The working principle of JWT includes three steps: generating JWT, verifying JWT and parsing Payload. 3. When using JWT for authentication in PHP, JWT can be generated and verified, and user role and permission information can be included in advanced usage. 4. Common errors include signature verification failure, token expiration, and payload oversized. Debugging skills include using debugging tools and logging. 5. Performance optimization and best practices include using appropriate signature algorithms, setting validity periods reasonably,

A string is a sequence of characters, including letters, numbers, and symbols. This tutorial will learn how to calculate the number of vowels in a given string in PHP using different methods. The vowels in English are a, e, i, o, u, and they can be uppercase or lowercase. What is a vowel? Vowels are alphabetic characters that represent a specific pronunciation. There are five vowels in English, including uppercase and lowercase: a, e, i, o, u Example 1 Input: String = "Tutorialspoint" Output: 6 explain The vowels in the string "Tutorialspoint" are u, o, i, a, o, i. There are 6 yuan in total

Static binding (static::) implements late static binding (LSB) in PHP, allowing calling classes to be referenced in static contexts rather than defining classes. 1) The parsing process is performed at runtime, 2) Look up the call class in the inheritance relationship, 3) It may bring performance overhead.

What are the magic methods of PHP? PHP's magic methods include: 1.\_\_construct, used to initialize objects; 2.\_\_destruct, used to clean up resources; 3.\_\_call, handle non-existent method calls; 4.\_\_get, implement dynamic attribute access; 5.\_\_set, implement dynamic attribute settings. These methods are automatically called in certain situations, improving code flexibility and efficiency.

PHP and Python each have their own advantages, and choose according to project requirements. 1.PHP is suitable for web development, especially for rapid development and maintenance of websites. 2. Python is suitable for data science, machine learning and artificial intelligence, with concise syntax and suitable for beginners.

PHP is widely used in e-commerce, content management systems and API development. 1) E-commerce: used for shopping cart function and payment processing. 2) Content management system: used for dynamic content generation and user management. 3) API development: used for RESTful API development and API security. Through performance optimization and best practices, the efficiency and maintainability of PHP applications are improved.

PHP is a scripting language widely used on the server side, especially suitable for web development. 1.PHP can embed HTML, process HTTP requests and responses, and supports a variety of databases. 2.PHP is used to generate dynamic web content, process form data, access databases, etc., with strong community support and open source resources. 3. PHP is an interpreted language, and the execution process includes lexical analysis, grammatical analysis, compilation and execution. 4.PHP can be combined with MySQL for advanced applications such as user registration systems. 5. When debugging PHP, you can use functions such as error_reporting() and var_dump(). 6. Optimize PHP code to use caching mechanisms, optimize database queries and use built-in functions. 7

PHP is still dynamic and still occupies an important position in the field of modern programming. 1) PHP's simplicity and powerful community support make it widely used in web development; 2) Its flexibility and stability make it outstanding in handling web forms, database operations and file processing; 3) PHP is constantly evolving and optimizing, suitable for beginners and experienced developers.
