PHP Notice: Trying to get property of non-object - Solution

During the PHP development process, we may encounter a common error message: Trying to get property of non-object. This error is usually caused when we try to access a property (or call a method) on a variable that is not an object type. This article will introduce you to the causes of this error and provide some solutions.

1. Error reason
When we try to obtain non-object attributes, PHP will issue this error prompt. This is usually because we mistakenly use a non-object type variable as an object, resulting in an error when accessing a property or method.

For example, in the following sample code, we create a variable $number of non-object type and try to get its properties:

$number = 10;
echo $number->value;

In this example, since $number is not a object, so trying to get its property $value will result in an error.

2. Solution
To solve this error, we need to ensure that the variable accessing the property or calling the method is an object. Here are some solutions:

1. Check variable type
   Before accessing a property or calling a method, we should check the type of the variable first. You can use PHP's built-in function is_object() to determine whether a variable is an object. If it is a non-object, you can choose not to access or call it.

The following is a sample code:

$number = 10;

if (is_object($number)) {
    echo $number->value;
} else {
    echo "變量不是一個對象";
}

In this example, we use the is_object() function to check the type of $number. If $number is an object, it is safe to access its property $value; otherwise, we print an error message.

2. Checking if a variable is empty
   Another common problem is trying to access a property of an empty variable. In this case, we can use the isset() function to check if the variable has been assigned a value.

The following is a sample code:

$number = null;

if (isset($number) && is_object($number)) {
    echo $number->value;
} else {
    echo "變量為空或不是一個對象";
}

In this example, we first use the isset() function to check whether $number is assigned a value. If it has been assigned a value and is an object type, it is safe to access its property $value; otherwise, we print an error message.

3. Check the assignment source of the variable
   Finally, we should also check the assignment source of the variable to make sure it is an object. When we return a variable from a function or method, sometimes we may accidentally return a non-object value.

The following is a sample code:

function getObject() {
    // 返回一個非對象的值
    return 10;
}

$object = getObject();

if (is_object($object)) {
    echo $object->value;
} else {
    echo "從getObject()函數(shù)獲取的值不是一個對象";
}

In this example, our function getObject() returns a value of non-object type. To solve this problem, we need to ensure that the function returns an object in all cases.

Summary:
In PHP development, "Trying to get property of non-object" errors are usually caused by trying to access properties or call methods on variables of non-object types. To solve this problem, we can avoid this error by checking the type of the variable, checking whether the variable is empty, and checking the source of the variable's assignment.

I hope the solutions in this article can help you solve common errors in PHP and improve your development efficiency!

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