How is the execution order of PHP functions determined?

The function execution order is determined by the definition order, calling order, nesting and return. The function defined first is executed first. The order of calling determines the order of execution. Internal functions are executed first. Function calls will block the current execution until the function returns.

#How is the execution order of PHP functions determined?

In PHP, the function execution order is determined by the following factors:

• Definition order: The function defined first will be executed first.
• Calling order: The order in which functions are called in the script.
• Nesting: When a function is nested within a function, the inner function will be executed first.
• Return: The function call will block the current execution until the function completes and returns the result.

Practical case

Consider the following code:

function outer() {
    echo "Outer function started.\n";
    inner();
    echo "Outer function ended.\n";
}

function inner() {
    echo "Inner function started.\n";
    echo "Inner function ended.\n";
}

outer();

Execution order:

1. Definitionouter() function.
2. Definition inner() function.
3. Call the outer() function.

4. Execution outer() Code inside the function:

   • Output "Outer function started.\n".
   • Call the inner() function.

5. Execute inner() Code inside the function:

   • Output "Inner function started.\n".
   • Output "Inner function ended.\n".
6. Return to the outer() function.

7. Continue execution outer() Code inside the function:

   • Output "Outer function ended.\n".

Output:

Outer function started.
Inner function started.
Inner function ended.
Outer function ended.

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