Parameter passing and return value types of PHP functions

Parameter passing in PHP has two methods: value passing and reference passing. The return value type can specify the returned data type. Passing by value: The function handles a copy of the parameter value, and modification of the parameter does not affect the variable of the calling function. Pass by reference: The function directly handles the address of the variable in the calling function, and modification of parameters will affect the variables of the calling function. Supported return value types include int, float, string, array, object, callable, and void.

Parameter passing and return value type of PHP function

Parameter passing

PHP functions can receive parameters using pass-by-value or pass-by-reference.

• Value passing: Functions work with copies of parameter values. Any changes made to the parameters will not affect the variables of the calling function.
• Pass by reference: The function directly handles the memory address of the variable in the calling function. Any changes made to the parameters will affect the variables in the calling function.

Usage:

In a function definition, use the & symbol before the parameter name to enable passing by reference.

For example:

function addByReference(&$num) {
  $num++;
}

Return value type

PHP functions can also specify the return value type. This means that when you return a value from a function, PHP checks the type of the value and casts it to match the specified type.

Syntax:

function function_name(param_type $param_name): return_type {
  // 函数代码
}

Supported types:

PHP supports the following return types:

• int: Integer
• float: Floating point number
• string: String
• array：array
• object：object
• callable：callable (function)
• void: No return type

##For example:

function getSum(int $a, int $b): int {
  return $a + $b;
}

Actual case

Value passing example:

<?php

$num = 10;

function add($num) {
  $num++;
}

add($num);

echo $num; // 输出：10，因为参数是按值传递的

?>

Reference passing example:

Return value type example:

<?php

function getGreeting(string $name): string {
  return "Hello, $name!";
}

$greeting = getGreeting("John");

echo $greeting; // 输出：Hello, John!

?>

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