strange question about PHP convert string to int

im trying to convert string to integer but return 0 or wrong number.
Below is the code i have tested.
Anyone know why?
Thanks

<?php
echo gettype(0x55)."\n"; //type is integer
echo 0x55."\n"; //this is correct
echo (int)"0x55"."\n"; //why 0?
echo intval("0x55"); //why 0?

return

integer
85
0
0

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>Solution :

By default, intval() parses base 10, so it ignores the 0x prefix.

If you specify the base as 0, it will determine the base dynamically from the string prefix: 0x means hex, 0 means octal.

So use intval("0x55", 0).

DEMO

I don’t think there’s any equivalent for the typecast syntax (int).