Detailed explanation of the usage of function class_exists in PHP to determine whether a class exists

This article mainly introduces the usage of PHP function class_exists to determine whether a class exists. The example analyzes the application of PHP to determine whether a class exists. For automatically loading classes and the existence judgment before class instantiation It is said that it is of great practical value. Friends in need can refer to

. This article analyzes the usage of the function class_exists in PHP to determine whether a class exists. Share it with everyone for your reference. The details are as follows:

If we want to judge whether a class can be used, we can first use the class_exists function to judge. Let's look at a few examples.

bool class_exists ( string $class_name [, bool $autoload = true ] )
This function checks whether the given class is defined. This function checks whether or not the given class has been defined.
Returns true if class_name is a defined class, otherwise returns false.

Examples are as follows:

function autoload($class)
{
    include($class . '.php');
    // check to see whether the include declared the class
    if (!class_exists($class, false)) {
        trigger_error("unable to load class: $class", e_user_warning);
    }
}
if (class_exists('myclass')) {
    $myclass = new myclass();
}

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