Questions about assignment-php Tutorial

Ask questions about assignment. Ask the experts to answer the following question $ str5012325658; $ str602556566; (float) $ str7 $ str5-$ str6; the result of echo is :. $ str7. & quot; & lt; p & gt; & quot; why are the output octal numbers in different formats from those in $ str5 and $ str6? How can I change the number of outputs to the number of 8 bytes ???? Ask questions about assignment.
Please answer the following questions

$ Str5 = 012325658;
$ Str6 = 02556566;
(Float) $ str7 = $ str5-$ str6;

Echo 'octal sequence result: '. $ str7 ."

"; // Why is the output octal number format different from the preceding $ str5 and $ str6 formats? How can I change the number of outputs to the number of 8 bytes ???? Unset ($ str7 );

Echo 'octal sequence result: '. $ str7; why is the value type null ??
If ($ str7 = null)
{
Echo '$ str7 value is Null ';
}
Else
{Echo '$ str7 value is 0 ';}
$ Str9 = null
$ Str10 = $ str9;
Echo '$ str10 value:'. $ str10; // why is $ str9 assigned to $ str10 ?? Are the connected values null? Why is it wrong ??

------ Solution --------------------
Printf ("% o", $ str7 );

// Or
Decoct ($ str7 );
------ Solution --------------------
$ Str9 = null;
$ Str10 = $ str9;
Echo '$ str10 value:'. $ str10;
The first sentence contains a semicolon.