How Php Code Is Parsed

PHP Programming

As a web developer, understanding how PHP code is parsed is essential for writing efficient and effective code. PHP is a popular server-side scripting language used for web development. When a PHP file is requested by a client’s browser, the server processes the PHP code and generates HTML output, which is then sent back to the client’s browser. In this article, I will dive deep into the process of how PHP code is parsed.

Lexical Analysis

The first step in parsing PHP code is lexical analysis, also known as tokenizing. During this step, the PHP code is broken down into smaller units called tokens, which include keywords, variables, function names, operators, and literals. The tokenizer reads the PHP code character by character and identifies each token. This step helps in identifying the structure of the PHP code.

Abstract Syntax Tree

Once the PHP code has been tokenized, the next step is to create an Abstract Syntax Tree (AST). The AST represents the structure and semantics of the PHP code. It is a hierarchical representation of the code, where each node represents a specific construct, such as a function call or a loop. The AST is useful for understanding the flow of the code and evaluating its correctness.

Compilation and Optimization

After the AST is generated, the PHP code is compiled into opcodes, which are low-level instructions that the PHP engine can execute. During this process, the PHP engine performs optimizations to improve the performance of the code. These optimizations may include inlining functions, removing dead code, or reordering instructions to reduce execution time.


Once the PHP code has been compiled, the opcodes are executed by the PHP engine. The PHP engine interprets each opcode and performs the corresponding operation, such as assigning values to variables, executing functions, or outputting HTML content. The execution of the PHP code follows the flow defined by the AST, executing each node in the correct order.


Understanding how PHP code is parsed is crucial for writing efficient and effective code. The process of parsing involves lexical analysis, creating an Abstract Syntax Tree, compilation, optimization, and execution. By understanding this process, you can optimize your PHP code and ensure its proper functioning. So next time you write PHP code, remember the journey it goes through before it generates the desired output for your web application.