PHP integer and string add-in

There are several kinds of algorithms,
For example: $tr = ' aaaaa '; Turn into 0

$tr = ' A123AA ';   Turn into  0

$tr = ' 22aaa ';   Turn into  22

That is, when matched to a string, not shaped, the match continues until the character is encountered and all subsequent transitions to 0are added to the front.

Example 1:

$str = "123stringA";
$str 2 = "123XX797STRINGB";

$result = $str + $str 2; $result = 456 (123+123)

Example 2:

$str = "string123a";
$str 2 = "123XX797STRINGB";

$result = $str + $str 2; $result = 123

According to this principle, to convert a numeric string to a numeric value you can add the original numeric string to a string that is converted to zero when adding (for example: stringABC12321).

Or, add to the number 0! ====> is operated by addition operations!

PHP integer and string add-in