PHP built-in functions are predefined functions implemented in the PHP parser to perform various common tasks and operations. These functions provide functions that developers can call directly without writing repetitive code to complete specific tasks. The working principle and underlying principle of these functions are implemented in the PHP parser, which can be divided into the following steps:
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Function call: When a built-in function is called in PHP code, the parser will find and locate the corresponding function code according to the function name.
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Parameter passing: A function may need to accept input parameters, and the parser will pass the parameters passed when calling it to the function's parameter list. Under the hood, PHP uses the stack to manage the passing of arguments to function calls.
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Function execution: After the parser locates the corresponding function code, it will execute the logical operations in the function body. Functions may perform calculations or operations with passed parameters.
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Return result: After the function is executed, it may return a result value. This result value can be a single value, or a complex type such as an array or an object. The parser passes the result returned by the function back to the caller.
Underlying principle: At the bottom of PHP, the implementation of built-in functions is usually an extended library function written in C or C++. These extension library functions are compiled into shared libraries (such as .dll files or .so files) and then loaded into memory when the PHP parser starts. When the PHP parser parses PHP code, when it encounters built-in function calls, it will directly call these predefined C/C++ functions.
This design and implementation has the following benefits:
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Performance optimization: Built-in functions written in C/C++ are usually faster than pure PHP functions because they are executed directly under the hood, reducing the overhead of interpreting and executing PHP code.
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Extensibility: The bottom layer of PHP can add new built-in functions by loading different extension libraries, which makes PHP highly flexible and extensible in function.
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Code reuse: By providing predefined functions, developers can avoid writing repetitive code and directly call built-in functions to complete common tasks.
Summary: PHP built-in functions are predefined functions implemented in the PHP parser, which provide various functions to facilitate the processing of common tasks by developers. The underlying principle of these functions is the extension library functions written in C/C++. These extension libraries are loaded into the memory when the PHP parser is started. When calling these functions in the PHP code, the underlying layer will directly execute the corresponding C/C++ functions. And return the result to the PHP parser. This design improves PHP's performance, flexibility, and code reusability.