php is_numeric零填充字符串（0000018）

Question

I have tested is_numeric on zero filled ints such 0000018 and it return true. The documentation says:

"Finds whether the given variable is numeric. Numeric strings consist of optional sign, any number of digits, optional decimal part and optional exponential part. Thus +0123.45e6 is a valid numeric value. Hexadecimal (e.g. 0xf4c3b00c), Binary (e.g. 0b10100111001), Octal (e.g. 0777) notation is allowed too but only without sign, decimal and exponential part."

Would this fall under the any number of digits part?

Answer 1

Both cases (string and the (invalid)octal number) will return true:

var_dump( is_numeric("0000018") );  //bool(true)
var_dump( is_numeric(0000018) );    //bool(true)

In the first case it's just a numeric string.

A quote from the manual (is_numeric()):

Returns TRUE if var is a number or a numeric string, FALSE otherwise.

In the second case it is a octal number, just a invalid one, so this will happen (From the manual Integer):

Warning: If an invalid digit is given in an octal integer (i.e. 8 or 9), the rest of the number is ignored.

Means in this case:

0000018 -> 000001 -> 1