Function to check if an integer is valid in PHP

Question

Is there a function in PHP that returns true if a string/int could be safely converted into an int? like so:

var_dump(f('1'));//returns true
var_dump(f(1));//returns true
var_dump(f('1.2'));//returns false
var_dump(f(-2));//returns true
var_dump(f('3x'));//returns false

I do not care about bases.
I checked out is_int, but is_int('4') returns false.
I could use a cast/intval, but:
intval('6x') returns 6, and intval('x') returns 0 as does intval(0) and intval('0')

Nice one, but i would prefer a more native solution, with documentation and whatnot. — user3004771
– user3004771, Commented May 16, 2014 at 17:51

John Conde · Accepted Answer · 2014-05-16 17:31:59Z

7

Use filter_var():

if (filter_var('1', FILTER_VALIDATE_INT)) {
     echo 'int'."<br>";
}
if (!filter_var('dog', FILTER_VALIDATE_INT)) {
     echo 'not int'."<br>";
}

Demo

answered May 16, 2014 at 17:31

John Conde

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Comments

Viktor Svensson · Accepted Answer · 2014-05-16 17:33:04Z

-2

The function is_int() is what you should use.

The reason why

is_int('4')

will return false is because it's not an integer. When you add quotes around the integer PHP will assume it's a string - hence the "false" return.

Try this out:

is_int(4)

answered May 16, 2014 at 17:33

Viktor Svensson

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4 Comments

user3004771 Over a year ago

Thanks, but the whole point is to check if a string is an int.

Viktor Svensson Over a year ago

A string is not an integer, that's just a basic datatype fact. Do you want to check if a string CONTAINS an integer?

user3004771 Over a year ago

No, a string is not an integer.But I want to check if a given string can be safely converted into an int.

Viktor Svensson Over a year ago

Alright, then you should listen to @John Conde. Good luck! :)

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