PHP Determines if {function/class/method/property} exists

1.php determine whether a system function or a function written by itself exists

BOOL Function_exists (string $function _name) determines whether a function has been defined, for example:

if (function_exists(' Curl_init ')) {    curl_init ();} Else {    echo ' not function Curl_init ';}

2.php determining whether a class exists

BOOL Class_exists (String $class _name [, bool $autoload = true]) checks whether a class has been defined, must return True, otherwise returns false, for example:

if (class_exists(' MySQL ')) {    $myclass=newMySQL();}

3.php determines whether a method within a class has been defined

BOOL Method_exists (mixed $object, string $method _name) checks for the existence of a method of a class, for example:

$directory=new  directory; if (! method_exists ($directory, ' read ') {    echo ' does not define the Read Method!} ';}

4.php determines whether a property within a class has been defined

BOOL property_exists ( mixed $class , string $property ) checks for the existence of a class's properties, for example:

$directory=new  directory; if (!property_exists ($directory, ' Li ')) {    echo ' does not have an LI attribute defined! ';}

PHP Determines if {function/class/method/property} exists