Comprehensive analysis of the underlying development principles of PHP7: revealing the compilation process and execution process of PHP

[Introduction]
PHP is a scripting language widely used in Web development. It is characterized by being easy to learn and use, highly flexible, and has relatively good performance on different platforms. Good compatibility. As the underlying engine of PHP, the release of PHP7 marks the further maturity and power of PHP. In this article, we will comprehensively analyze the underlying development principles of PHP7, reveal the secrets one by one from the compilation process to the execution process, and use code examples to deepen our understanding of these concepts.

[1. Compilation process]
The execution of PHP script language is based on the interpreter. Before running, PHP scripts need to be compiled into bytecode, which is then read and executed by the interpreter. PHP7 introduces a new just-in-time compiler (JIT) to improve performance.
The following is a simple example:

<?php
echo "Hello, PHP7!";
?>

First of all, during the compilation process of PHP, the PHP source code will first go through a series of lexical and syntactic analyzes to convert it into an abstract tree with semantic meaning. Syntax tree (AST). The compiler checks for syntax errors such as mismatched brackets, undefined variables, etc.

Then, the compiler converts the AST into a low-level intermediate representation language (ie bytecode), which can improve the execution efficiency of the code. Bytecode is a binary representation similar to machine code, which is closer to the underlying computer hardware than source code.

Finally, the PHP engine provides an interpreter to read and execute bytecode and output the results. More importantly, PHP7 introduces a JIT compiler, a just-in-time compiler, which can compile commonly used bytecodes into local machine code, thus further improving the performance of PHP.

[2. Execution Process]
After understanding the compilation process, let’s take a look at the execution process of PHP7. The execution process of PHP script can be simplified to the following steps:

1. Source code parsing: Parse the source code into an abstract syntax tree.
2. Bytecode generation: Convert abstract syntax tree into bytecode.
3. JIT compilation: The JIT compiler compiles bytecode into machine code to improve performance.
4. Execute bytecode: The PHP engine interpreter reads the bytecode and executes it, and outputs the result.

The following is an example showing the execution flow of a PHP script:

<?php
function sum($a, $b) {
  return $a + $b;
}

$num1 = 3;
$num2 = 4;
$result = sum($num1, $num2);

echo "The result is: " . $result;
?>

First, the source code parsing process parses this code into an abstract syntax tree. The bytecode generator then converts the abstract syntax tree into bytecode.

Next, the JIT compiler performs just-in-time compilation of the bytecode and converts it into local machine code.

Finally, the PHP interpreter reads and executes the bytecode and outputs the result. In this example, "The result is: 7" will be output.

[Conclusion]
Through a comprehensive analysis of the underlying development principles of PHP7, we understand the compilation process and execution process of the PHP script language. Understanding these concepts is crucial to understanding the underlying principles of PHP and optimizing PHP application performance. At the same time, through the demonstration of code examples, we have a deeper understanding of the specific applications of these concepts. I hope this article can inspire readers to further explore the underlying development principles of PHP7 and provide more powerful support for Web development.

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