Full analysis of the underlying development principles of PHP7: learn the design and implementation of compilers and interpreters

As a popular server-side scripting language, PHP7 is widely used in development for its efficiency and flexibility. However, to truly understand the working principles behind PHP7, you need to deeply study its underlying development principles, especially the design and implementation of compilers and interpreters. This article will comprehensively analyze the underlying development principles of PHP7 and help readers better understand the working mechanism of PHP7.

First of all, we need to understand the basic concepts of compilers and interpreters.

A compiler is a program that converts a high-level language (such as PHP) into a low-level language (such as machine code). The compiler takes the source code as input, and finally generates the target code through processes such as lexical analysis, syntax analysis, and semantic analysis. The target code can be machine code or intermediate code.

An interpreter is a program that executes source code line by line. The interpreter takes source code as input and parses and executes it line by line without converting the source code into machine code. The interpreter can directly run the source code in a specific environment, such as parsing and executing PHP code in the PHP interpreter.

In the underlying development of PHP7, the compiler and interpreter work closely together to complete the compilation and execution of the code.

First, the PHP7 compiler will perform lexical analysis and syntax analysis on the source code. Lexical analysis breaks down the source code into individual words (tokens), such as identifiers, keywords, operators, etc. Grammatical analysis combines words into a syntax tree according to grammatical rules.

Next, the compiler performs semantic analysis on the syntax tree. In the semantic analysis stage, the compiler will check the declaration and type of variables, check the definition of functions and classes, perform type inference, etc. The results of semantic analysis will serve as an interface between the compiler and the interpreter, helping the interpreter understand and execute the source code.

Once the semantic analysis is completed, the compiler will generate intermediate code based on the results of the semantic analysis. Intermediate code is an abstract, machine-independent representation of code. Intermediate code can be a sequence of instructions similar to assembly language, or it can be a form similar to bytecode. The intermediate code generation process can utilize various optimization techniques to improve execution efficiency and reduce code size.

After the compiler generates the intermediate code, it hands it to the interpreter for execution. The interpreter executes the source code one by one according to the instructions of the intermediate code. During the execution process, the interpreter will assign values ​​to variables, execute function and class definitions, perform calculations and control flow operations, etc. The interpreter converts the source code into a form that the machine can understand by parsing the intermediate code in real time.

In PHP7, the interpreter also introduced JIT (just-in-time compilation) technology to further improve the execution speed of the code. JIT technology can dynamically compile hot code (that is, frequently executed code) into machine code and cache it. The next time the same code is executed, the interpreter can directly execute the compiled machine code without parsing and executing the intermediate code again.

To summarize, the underlying development principles of PHP7 include the design and implementation of compilers and interpreters. The compiler is responsible for converting source code into intermediate code, and the interpreter is responsible for executing the intermediate code. The compiler generates intermediate code through lexical analysis, syntax analysis, semantic analysis and other processes, and the interpreter converts the source code into a form that the machine can understand by executing the intermediate code. JIT technology can further improve the execution speed of code.

By in-depth study of the underlying development principles of PHP7, we can better understand the working mechanism of PHP7, further optimize the performance of the program, and improve development efficiency. At the same time, for beginners, learning the design and implementation of compilers and interpreters is also a good way to improve basic computer knowledge. Therefore, in-depth study and mastery of the underlying development principles of PHP7 is a goal that every PHP developer should strive to pursue.

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