Undefinedvariable: strin

The output prompts "Notice: Undefinedvariable: strinfunction & nbsp; Call () {& nbsp; for ($ i0; $ I & lt; 10; $ I ++) & nbsp; & nbsp ;{& nbsp; & nbsp; & the output prompts "Notice: Undefined variable: str in" when an Undefined variable is displayed.
Function Call (){
For ($ I = 0; $ I <= 10; $ I ++)
{
$ Str. = $ I ."
";
}
Return $ str;
}

Echo Call ();

The output displays the Notice: Undefined variable prompt.
------ Solution --------------------
Notice: Undefined variable
Indicates that you have used the value of a variable without a value assignment.

In your $ str. = $ I ."
"; $ Str is not assigned a value when you first enter, so an error is reported.

Function Call (){
$ Str = ''; // This sentence cannot be fewer
For ($ I = 0; $ I <= 10; $ I ++)
{
$ Str. = $ I ."
";
}
Return $ str;
}

Echo Call ();