How does the parameter passing method of PHP functions affect code readability and maintainability?

The impact of parameter passing methods of PHP functions on code readability and maintainability

There are two ways to pass parameters in PHP : Passing by value and Passing by reference . Understanding the difference between these two approaches is critical to writing readable, maintainable code.

Passing value

• Principle: The function accepts a copy of the variable value, and changes to the copy will not affect the original variable.
• Advantages: Protect original variables from side effects and improve code predictability.
• Example:

function add_ten($num) {
    $num += 10;
}

$a = 5;
add_ten($a); // $a 保持为 5，因为函数接收到的是副本

Pass reference

• Principle: Function The variable is accessed directly instead of a copy, and any changes made to the parameter are reflected in the original variable.
• Advantages: Allows functions to modify variables outside the function, saving memory.
• Example:

function add_ten(&$num) {
    $num += 10;
}

$a = 5;
add_ten($a); // $a 变为 15，因为函数直接修改了原始变量

The impact of readability and maintainability

##Readable Characteristics:

• Passing by value: The function does not modify the original variable, making the code easier to understand and track.
• Passing by reference: The function can modify the original variable, and the code readability is reduced because it does not obviously indicate the modification of the external variable of the function.

Maintainability:

• Pass value: Prevent functions from accidentally modifying external variables and improve the maintainability of the code .
• Passing by reference: Since functions can see modifications to external variables, this may cause errors and debugging problems in the code.

Practical case

Consider a function that accepts an array and adds a new element:

function add_element($arr, $elem) {
    $arr[] = $elem; // 传值
}

function add_element_ref(&$arr, $elem) {
    $arr[] = $elem; // 传引用
}

Passing value: Adding elements does not affect the original array, keeping the code predictable and maintainable.

Pass by reference: Adding elements also modifies the original array, which may not be expected behavior, leading to errors that are difficult to diagnose.

Guidelines:

In general, it is recommended to use

pass-by-value when:

requires protection External variables are not affected by function side effects.
• Functions should not modify external variables.
• Avoid potential code obfuscation and debugging issues.

If you really need the function to modify external variables, please use

pass by reference, but use it with caution.

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