Argument function php Function arguments - Manual

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Function arguments

Information may be passed to functions via the argument danh mục, which is a comma-delimited các mục of expressions. The arguments are evaluated from left to right.

obatambeienwasirherbal.comhường supports passing arguments by value (the default), passing by reference, và default argument values. Variable-length argument lists and Named Arguments are also supported.

Example #1 Passing arrays to lớn functions

function takes_array($input)


As of 8.0.0, the các mục of function arguments may include a trailing comma, which will be ignored. That is particularly useful in cases where the menu of arguments is long or contains long variable names, making it convenient khổng lồ danh sách arguments vertically.

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Example #2 Function Argument List with trailing Comma

function takes_many_args(
$arg_with_default 5,
$again "a default string"// This trailing comma was not permitted before 8.0.0.


As of 8.0.0, passing mandatory arguments after optional arguments is deprecated. This can generally be resolved by dropping the mặc định value. One exception khổng lồ this rule are arguments of the size Type $param = null, where the null mặc định makes the type implicitly nullable. This usage remains allowed, though it is recommended to use an explicit nullable type instead.

Example #3 Passing optional arguments after mandatory arguments

function foo($a = <>, $b)       // After

function bar(A $a null$b)        // Recommended

Passing arguments by reference

By mặc định, function arguments are passed by value (so that if the value of the argument within the function is changed, it does not get changed outside of the function). To allow a function to modify its arguments, they must be passed by reference.

To have an argument lớn a function always passed by reference, prepend an ampersand (&) to lớn the argument name in the function definition:

Example #4 Passing function parameters by reference

function add_some_extra(&$string)

$str "This is a string, ";
$str;    // outputs "This is a string, and something extra."

It is an error lớn pass a value as argument which is supposed lớn be passed by reference.

Default argument values

A function may define C++-style default values for scalar arguments as follows:

Example #5 Use of default parameters in functions

function makecoffee($type "cappuccino")