Arrow functions are suitable for scenarios with single expressions, simple callbacks and improved readability; 2. Anonymous functions are suitable for scenarios with multi-line logic, complex control flow, referencing external variables and using yield generators; therefore, you should choose according to specific needs: simple scenarios prioritize arrow functions to improve code simplicity, while complex scenarios use anonymous functions to obtain full functional support.

PHP's anonymous functions (Anonymous Functions) and arrow functions (Arrow Functions) are both used to create functions that do not require name and are often used in callback scenarios. Although they overlap in functionality, there are obvious differences in syntax, scoped processing, and usage habits. Let’s compare these two in depth to help you make more appropriate choices in actual development.

1. Basic syntax comparison

Anonymous functions (Closure) are defined using function keyword, and the syntax is relatively lengthy but flexible:

 $multiplier = 2;
$double = function ($x) use ($multiplier) {
    return $x * $multiplier;
};

echo $double(5); // Output: 10

Arrow function uses the fn keyword and => syntax, which is more concise:

 $multiplier = 2;
$double = fn($x) => $x * $multiplier;

echo $double(5); // Output: 10

As you can see, the arrow function eliminates function , return and use keywords, making the code more compact.

2. Variable scope processing ( use vs automatic inheritance)

This is one of the most critical differences between the two.

• Anonymous function : use must be used explicitly to introduce parent scope variables, otherwise it will not be accessible.

 $factor = 3;
$func = function ($x) use ($factor) {
    return $x * $factor; // must use to access $factor
};

• Arrow function : Automatically capture variables in the parent scope "by value", without use .

 $factor = 3;
$func = fn($x) => $x * $factor; // Automatically capture $factor

?? Note: The arrow function captures the value of the variable, not a reference. If you need to modify external variables, the arrow function cannot do it (anonymous functions can be passed through use (&$var) ).

For example, want to modify external variables through closures:

 $count = 0;
$increment = function () use (&$count) {
    $count ;
};

$increment();
echo $count; // Output: 1

This requirement cannot be implemented with arrow functions because reference capture is not supported.

3. Supported syntax features

Although the arrow function is concise, it has limited functions. The following are features that are supported by anonymous functions but not supported by arrow functions:

• Multi-line statement (arrow functions can only be single expressions)
• Use control structures other than return (such as if , foreach , throw , etc.)
• Use yield (generator)
• Use static modification
• More complex parameter processing (although the parameter syntax is the same, but the context limits are more)

Error example (arrow function cannot write multiple lines) :

 // ? Syntax error $func = fn($x) => {
    $y = $x * 2;
    return $y 1;
};

Correct way (anonymous functions must be used) :

 $func = function ($x) {
    $y = $x * 2;
    return $y 1;
};

Therefore, arrow functions only apply to simple logic of "single expression".

4. Performance and readability

• Performance : The performance difference between the two is extremely small. PHP internally optimizes the arrow function, which can be almost ignored in actual scenarios.
• Readability : Arrow functions significantly improve readability in simple callbacks, especially in scenarios such as array_map and usort :

 // Use the anonymous function $names = array_map(function ($user) use ($prefix) {
    return $prefix . $user['name'];
}, $users);

// Use arrow functions (more clearer)
$names = array_map(fn($user) => $prefix . $user['name'], $users);

The code is cleaner and the logic is clear at a glance.

Summary: When to use which one?

Basically that's it. Instead of replacing anonymous functions, arrow functions provide more elegant syntactic sugar for "simple scenarios". Mastering the differences between the two will allow you to write clearer and more efficient PHP code.

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