PHP preg_match() to validate international phone number by meeting specific criteria

I want to validate a given international phone number using php preg_match() function following these rules: - Only digits allowed, no special chars and white spaces

phone number must starts always with '00' not +
phone number length should be not lower than 11 symbols

So far I have this which checks the beginning of the string:

preg_match("~^00\d+$~", $_POST['phone'])

but if I pass: 00014568978945 it will accept it as correct as it checks to has min '00' but third '0' makes the phone invalid..

How should look like the full preg_match() condition to check for above requirements? Thank you in advance for your time!

Solution

I suggest

 ~^00[1-9]\d{8,}$~D

See the regex demo.

Details:

^00 - starts with two 0s, then
[1-9] - a non-zero digit, and then
\d{8,} - any 8 or more digits
$ - end of string.

Since you are validating, I also included D PCRE_DOLLAR_ENDONLY modifier that forces the $ anchor to always match the very end of the string.