PHP type constraints

: This article mainly introduces the type constraints of PHP. For more information about PHP tutorials, see.

In a strong type language, type constraints are syntactically required. when defining a variable, you must specify the type and later only store this type of data;

Php is a weak type, which does not need to specify the type for the variable and can store any type after it. However, in the new language of php, in some specific scenarios, syntax constraints can also be applied to certain types.

• Special occasion: parameter variables of functions (methods)
• Specific types: Object type (class name), interface type (interface name), array type (array), function type (callable)

That is, you can set the required type for function (method) parameters. Only objects, interfaces, arrays, and functions can be restricted.

Functionf (class name $ p) {}// required parameter can only use the class object functionf (interface name $ p) {} // this parameter must use only the functionf (arrary $ p) {} // object that implements this interface. this parameter must use only the array functionf (callable $ p) // this parameter must be a function (method), which is called a callback function (method)

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The above introduces the type constraints of PHP, including the content, and hope to be helpful to friends who are interested in PHP tutorials.