inconsistency in converting string to integer, when string is hex, prefixed with '0x'

Question

Using PHP 5.3.5. Not sure how this works on other versions.

I\'m confused about using strings that hold numbers, e.g., \'0x4B0\' or \'1.2e3\'

Answer 1

Is there (or, rather, should there be) any relation between is_numeric() and the way how PHP treats strings when they are used as numbers?

There is no datatype called numeric in PHP, the is_numeric() function is more of a test for something that can be interpreted as number by PHP.

As far as such number interpreting is concerned, adding a + in front of the value will actually make PHP to convert it into a number:

$int = +'0x4B0';
$float = +'1.2e3';

You find this explained in the manual for string, look for the section String conversion to numbers.

As it's triggered by an operator, I don't see any need why there should be a function in PHP that does the same. That would be superfluous.

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Internally PHP uses a function called zendi_convert_scalar_to_number for the add operator (assumable +) that will make use of is_numeric_string to obtain the number.

The exact same function is called internally by is_numeric() when used with strings.

So to trigger the native conversion function, I would just use the + operator. This will ensure that you'll get back the numeric pseudo-type (int or float).

Ref: /Zend/zend_operators.c; /ext/standard/type.c