How PHP functions execute

PHP functions are executed by creating a new execution environment containing local variables, scopes and parameters: parsing the function call statement. Create an execution stack frame. Initialize local variables. Execute the function body. Return results. Exit function.

Execution principle of PHP function

Overview of principle

PHP function is a A block of code that can be called from other places in the program. When a function is called, it creates a new execution environment with local variables, local scope, and its own parameters.

Specifically, function execution involves the following steps:

1. Parsing the function call: The PHP parser parses the function call statement to determine the function name to be called and the passed parameters.
2. Create execution stack: Create a new function execution stack frame. The stack frame contains local variables, parameters, and the return address of the current function.
3. Initialize local variables: According to the function definition, initialize the local variables of the function.
4. Execute function body: Execute the code in the function body, which may include conditional judgments, loops and function calls.
5. Return result: When the function completes execution or encounters a return statement, it will return a value or null.
6. Exit function: Destroy the execution stack frame of the function and return to the code that called the function.

Practical case

Consider a simple function that calculates the sum of two numbers:

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

// 调用函数
$result = sum(10, 20);
echo $result; // 输出：30

When calling sum function, PHP will perform the following steps:

1. Parse the function call statement and determine the sum function name and parameters 10 and 20 .
2. Create a new stack frame. The frame contains the variables $a and $b and initializes their values.
3. Execute the function body, calculate the sum of $a and $b and store it in $sum.
4. Returns the value of $sum, here is 30.
5. Destroy the stack frame and return to the code of the calling function.

This shows the basic steps of PHP function execution principle, which involves creating an execution stack frame, initializing local variables, executing the function body and returning the result.

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