What does ? in php mean?

The "?" symbol in PHP represents a nullable type, allowing the value of the variable to be null. Nullable type variables can be assigned a null value, and PHP will automatically check whether the variable is null and handle it accordingly. The advantages of nullable types include enhanced type safety, improved readability, and support for chained operations.

"?" in PHP: Nullable type

What is "?"

In PHP, the "?" symbol represents a nullable type, which allows the value of a variable to be empty (that is, not set).

How nullable types work

Variables with nullable types can be assigned a null value, that is, null. As you proceed, PHP will automatically check if the variable is empty and handle it accordingly.

Example:

<code class="php">$name = null; // 可空类型变量

if (!empty($name)) {
  echo "姓名：{$name}";
} else {
  echo "姓名为空";
}</code>

In this example, the variable $name is declared as a nullable type and assigned a null value. If $name is not null (that is, not null), the name is printed; otherwise, a message is printed indicating that the name is null.

Advantages of nullable types

• Enhanced type safety: Prevent null from being accidentally assigned to non-null type variables.
• Improve code readability: clearly indicate that variables may be empty to avoid confusion and errors.
• Support chained operations: allows a series of operations on nullable type variables without causing errors.

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