php sprintf function usage php floating point number format

sprintf(" %9.3f", 3.1415926); // Right alignment: If there are not enough digits, use spaces to complete it. Result: "3.142"
sprintf(" %-9.3f", 3.1415926); //Left-aligned: If there are not enough digits, use spaces to complete it. Result: "3.142 "
sprintf(" %.3f", 3.1415926); //Do not specify the total width, result: "3.142"

Note:

$num = 100;
sprintf("%.2f", $num );
sprintf("%.2f", (double)$num);

above Are the two results really the same? Although it looks the same, the following reasons may be enlightening. Cause analysis: When the parameter is pushed onto the stack, the caller does not know that the format control character corresponding to num is "%f". When the function is executed, the function itself does not know that what was pushed onto the stack was an integer, so the poor 4 bytes storing the integer $num are forcibly interpreted as a floating point number format, and the whole thing is messed up.