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How to check that a string is an int, but not a double, etc.?

Asked 2010-01-06T10:21:32.163
207

PHP has an intval() function that will convert a string to an integer. However I want to check that the string is an integer beforehand, so that I can give a helpful error message to the user if it's wrong. PHP has is_int(), but that returns false for string like "2".

PHP has the is_numeric() function, but that will return true if the number is a double. I want something that will return false for a double, but true for an int.

e.g.:

my_is_int("2") == TRUE
my_is_int("2.1") == FALSE
php string casting types int
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1 Answer

131

filter_var should do it:

var_dump(filter_var('2', FILTER_VALIDATE_INT));   // 2
var_dump(filter_var('2.0', FILTER_VALIDATE_INT)); // false
var_dump(filter_var('2.1', FILTER_VALIDATE_INT)); // false

but

var_dump(filter_var(2, FILTER_VALIDATE_INT));     // 2
var_dump(filter_var(2.0, FILTER_VALIDATE_INT));   // 2
var_dump(filter_var(2.1, FILTER_VALIDATE_INT));   // false

If you just want Booleans as return values, wrap it into a function, e.g.

function validatesAsInt($number)
{
    $number = filter_var($number, FILTER_VALIDATE_INT);
    return ($number !== FALSE);
}
answered 2010-01-06T10:38:15.263

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