PHP learning: in-depth understanding of is_callable() and method_exists() functions

This article mainly introduces the is_callable() and method_exists() functions in PHP, which has high learning value. Interested friends can learn about it.

1. Function analysis

##is_callable()

Definition:

(PHP 4 >= 4.0.6, PHP 5, PHP 7)

is_callable — Detect whether the parameter is a legal callable structure

bool is_callable ( callable $name [, bool $syntax_only = false [, string &$callable_name ]] )

##Verify whether the content of the variable can be called as a function . This can check for a variable containing a valid function name, or an array containing a correctly encoded object and function name.

Parameters:

##name

The callback function to check.

syntax_only

If set to

TRUE

, this function only verifies name May be a function or method. It simply rejects non-characters, or does not contain a valid structure that can be used in the callback function. Valid should contain two elements, the first is an object or character, and the second element is a character.

callable_name

Accepts "callable name". The example below is "someClass::someMethod". Note that although someClass::SomeMethod() is meant to be a callable static method, this is not the case in the example.

Return value: ##If name

can be called Returns

TRUE, otherwise returns FALSE. Reference:

http://php.net/manual/zh/function.is-callable.php2. Function test

Test one:

echo &#39;<pre >&#39;;
$func = function ($a)
{
    echo $a;
};
$re = is_callable($func, true, $callable_name1);
echo &#39;<hr />&#39;;
$re1 = is_callable($func, false, $callable_name2);

//结果
bool(true)
string(17) "Closure::__invoke"
-------------------------------------
bool(true)
string(17) "Closure::__invoke"

Test results:

For anonymous functions, after passing in the function variable, parameter twosyntax_only

true and false, the printing results are the same. ##Test 2:

function c_b($d)
{
    echo $d;
}
$re = is_callable('c_b', false, $callable_name1);
$re1 = is_callable('c_b', true, $callable_name2);
var_dump($re);
echo &#39;<hr />&#39;;
var_dump($re1);
echo &#39;<hr />&#39;;
var_dump($callable_name1);
echo &#39;<hr />&#39;;
var_dump($callable_name2);
//结果
bool(true)
----------------
bool(true)
----------------
string(3) "c_b"
----------------
string(3) "c_b"

Test result:

For general functions, After passing in the function name, parameter two

syntax_only true and false

, the printed results are the same.

Test three:

class Person
{
    public static function get($a)
    {
        echo $a;
    }

    protected function _set()
    {
        echo 1;
    }
}
$p = new Person();

$re = is_callable([$p, 'get'], false, $callable_name1);
$re1 = is_callable([$p, 'get'], true, $callable_name2);
var_dump($re);
echo &#39;<hr />&#39;;
var_dump($re1);
echo &#39;<hr />&#39;;
var_dump($callable_name1);
echo &#39;<hr />&#39;;
var_dump($callable_name2);
//结果
bool(true)
-----------------
bool(true)
-----------------
string(11) "Person::get"
---------------------------
string(11) "Person::get"

Test result:

For Class method, the parameters are in array structure (class object or class name method name), parameter two syntax_only true and false

, the printing result is the same.

Test four:

$a = 'i am string';
$re = is_callable($a, false, $callable_name1);
$re1 = is_callable($a, true, $callable_name2);
var_dump($re);
echo &#39;<hr />&#39;;
var_dump($re1);
echo &#39;<hr />&#39;;
var_dump($callable_name1);
echo &#39;<hr />&#39;;
var_dump($callable_name2);
//结果
bool(false)
----------------
bool(true)
----------------
string(11) "i am string"
-------------------------
string(11) "i am string"

Test result:

对于传入的验证name，如果syntax_only 设置为true，它验证传入name是否是字符串，是否含有非法字符，如果不含有，则返回true，它并不会验证name是否为合法调用结构。

测试五：

$re = is_callable(['Class', 'Method'], false, $callable_name1);
$re1 = is_callable(['Class', 'Method'], true, $callable_name2);
var_dump($re);
echo &#39;<hr />&#39;;
var_dump($re1);
echo &#39;<hr />&#39;;
var_dump($callable_name1);
echo &#39;<hr />&#39;;
var_dump($callable_name2);
//结果
bool(false)
--------------
bool(true)
--------------
string(13) "Class::Method"
-----------------------------
string(13) "Class::Method"

测试结果：

对于传入的验证name，如果syntax_only 设置为true，它只验证传入name是否是字符串，是否含有非法字符或是否为数组参数字符串1 + 字符串二，如果符合条件，则返回true，它并不会验证name是否为合法调用结构。否者返回false；

测试六：

class Person
{
    public static function get($a)
    {
        echo $a;
    }

    protected function _set()
    {
        echo 1;
    }
}
$p = new Person();
$re = is_callable([$p, '_set'], false);
var_dump($re);
echo &#39;<hr />&#39;;
$re1 = method_exists($p, &#39;_set&#39;);
var_dump($re1);
//结果
bool(false)
------------
bool(true)

测试结果：

对于函数is_callable() 来说，如果验证的类方法，访问修饰符为protected或private 则返回false。

对于method_exists() 来说，则不受访问修饰符的影响，只要类方法存在，则返回true。

 三、总结、

1、is_callable() 函数，可传入的name类型有：函数字符串，匿名函数变量，类或类对象和方法名称组成的数组。其函数第二参数，如果是true，则只验证name是否是字符串或则是类或字符串1（类对象）和字符串二（方法名称）组成的数组。而不验证name是否为合法调用结构。如果是false，则验证name是否为合法调用结构。

2、method_exists() 函数，不受访问修饰符的影响，只要类方法存在，则返回true。函数is_callable()来说，如果验证的类方法，访问修饰符为protected或private 则返回false。

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