Checking if a variable is an integer in PHP

Question

I have the following code       page     GET  p         if  page                       page   1            if is int  page     false                setcookie  error    Invalid page    time   3600           header  location somethingwentwrong php            die                else continue with code   which I am going to use for looking at different  pages  of a database  results 1-10  11-20  etc   I can t seem to get the is int   function to work correctly  however  Putting  1  into the url  noobs php p 1  gives me the invalid page error  as well as something like  asdf

User · Answer

When i start reading it i did notice that you guys forgot about abvious think like type of to check if we have int, string, null or Boolean. So i think gettype() should be as 1st answer. Explain: So if we have $test = [1,w2,3.45,sasd]; we start test it

foreach ($test as $value) {
        $check = gettype($value);
        if($check == 'integer'){
            echo "This var is int\r\n";
        }
        if($check != 'integer'){
            echo "This var is {$check}\r\n";
        }
}

And output:

> This var is int 
> This var is string 
> This var is double 
> This var is string

I think this is easiest way to check if our var is int, string, double or Boolean.

User · Answer

Using is numeric   for checking if a variable is an integer is a bad idea  This function will return TRUE for 3 14 for example  It s not the expected behavior   To do this correctly  you can use one of these options   Considering this variables array      variables          TEST 0    gt  0       TEST 1    gt  42       TEST 2    gt  4 2       TEST 3    gt   42       TEST 4    gt  42        TEST 5    gt   42        TEST 6    gt   a42        TEST 7    gt   42a        TEST 8    gt  0x24       TEST 9    gt  1337e0      The first option  FILTER VALIDATE INT way       Check if your variable is an integer if   filter var  variable  FILTER VALIDATE INT      false       echo  Your variable is not an integer       Output    TEST 0   0  type integer  is an integer   TEST 1   42  type integer  is an integer   TEST 2   4 2  type double  is not an integer   TEST 3   0 42  type double  is not an integer   TEST 4   42  type double  is an integer   TEST 5   42  type string  is an integer   TEST 6   a42  type string  is not an integer   TEST 7   42a  type string  is not an integer   TEST 8   36  type integer  is an integer   TEST 9   1337  type double  is an integer     The second option  CASTING COMPARISON way       Check if your variable is an integer if   strval  variable      strval intval  variable         echo  Your variable is not an integer       Output    TEST 0   0  type integer  is an integer   TEST 1   42  type integer  is an integer   TEST 2   4 2  type double  is not an integer   TEST 3   0 42  type double  is not an integer   TEST 4   42  type double  is an integer   TEST 5   42  type string  is an integer   TEST 6   a42  type string  is not an integer   TEST 7   42a  type string  is not an integer   TEST 8   36  type integer  is an integer   TEST 9   1337  type double  is an integer     The third option  CTYPE DIGIT way       Check if your variable is an integer if     ctype digit strval  variable         echo  Your variable is not an integer       Output    TEST 0   0  type integer  is an integer   TEST 1   42  type integer  is an integer   TEST 2   4 2  type double  is not an integer   TEST 3   0 42  type double  is not an integer   TEST 4   42  type double  is an integer   TEST 5   42  type string  is an integer   TEST 6   a42  type string  is not an integer   TEST 7   42a  type string  is not an integer   TEST 8   36  type integer  is an integer   TEST 9   1337  type double  is an integer     The fourth option  REGEX way       Check if your variable is an integer if     preg match     d       variable        echo  Your variable is not an integer       Output    TEST 0   0  type integer  is an integer   TEST 1   42  type integer  is an integer   TEST 2   4 2  type double  is not an integer   TEST 3   0 42  type double  is not an integer   TEST 4   42  type double  is an integer   TEST 5   42  type string  is an integer   TEST 6   a42  type string  is not an integer   TEST 7   42a  type string  is not an integer   TEST 8   36  type integer  is an integer   TEST 9   1337  type double  is an integer

User · Answer

Values   GET are always strings  ndash  that s what GET paramters come as  Therefore  is int   GET       is always false   You can test if a string consists only of digits i e  could be interpreted as a number  with is numeric

User · Answer

page    isset   GET  p       int   GET  p     1   if   page  gt  0              Try casting and checking if it s a number initially

User · Answer

All   GET parameters have a string datatype  therefore  is int will always return false    You can see this by calling var dump   var dump   GET  p        string 2   54    Using is numeric will provide the desired result  mind you  that allows values such as  0x24

User · Answer

Best anwser is not correct  is numeric   returns true for integer AND all numeric forms like  9 1   For integer only you can use the unfriendly preg match     d       var  or the explicit and 2 times faster comparison    if   int   var     var            var is an integer     PS  i know this is an old post but still the third in google looking for  php is integer

User · Answer

Use is int  var   Here is tutorial about is int

User · Answer

I had a similar problem just now   You can use the filter input   function with FILTER VALIDATE INT and FILTER NULL ON FAILURE to filter only integer values out of the   GET variable  Works pretty accurately      Check out my question here  How to check whether a variable in   GET Array is an integer

User · Answer

When the browser sends p in the querystring  it is received as a string  not an int   is int   will therefore always return false   Instead try is numeric   or ctype digit

User · Answer

You could try using a casting operator to convert it to an integer    page    int    GET  p     if  page               page   1    if empty  page       page        setcookie  error    Invalid page    time   3600       header  location somethingwentwrong php        die        else continue with code

User · Answer

An integer starting with 0 will cause fatal error as of PHP 7  because it might interpret it as an octal character      Invalid octal literals      Previously  octal literals that contained invalid numbers were   silently truncated  0128 was taken as 012   Now  an invalid octal   literal will cause a parse error    So you might want to remove leading zeros from your integer  first    var   ltrim  var  0

User · Answer

doctormad s solution is not correct  try this    var    1a   if   int   var     var        var dump   var is an integer  really         this prints     1a is an integer  really     use filter var   with FILTER VALIDATE INT argument   data   Array  0    1    1a    1 1    1e    0x24   PHP INT MAX 1   array walk  data  function   num    is int   filter var  num  FILTER VALIDATE INT   if   is int     false  var dump   num is not int          this prints  1a is not int  1 1 is not int 1e is not int 0x24 is not int 9 2233720368548E 18 is not int

User · Answer

Just for kicks  I tested out a few of the mentioned methods  plus one I ve used as my go to solution for years when I know my input is a positive number or string equivalent   I tested this with 125 000 iterations  with each iteration passing in the same set of variable types and values   Method 1  is int  value     ctype digit  value  Method 2   string  int  value     string  value Method 3  strval intval  value       strval  value  Method 4  ctype digit strval  value   Method 5  filter var  value  FILTER VALIDATE INT      FALSE Method 6  is int  value     ctype digit  value      is string  value   amp  amp   value 0       -   amp  amp  filter var  value  FILTER VALIDATE INT      FALSE   Method 1  0 0552167892456 Method 2  0 126773834229 Method 3  0 143012046814 Method 4  0 0979189872742 Method 5  0 112988948822 Method 6  0 0858821868896     I didn t even test the regex  I mean  seriously    regex for this    Things to note  Method 4 always returns false for negative numbers  negative integer or string equivalent   so is a good method to consistently detect that a value is a positive integer  Method 1 returns true for a negative integer  but false for a string equivalent of a negative integer  so don t use this method unless you are certain your input will never contain a negative number in string or integer form  and that if it does  your process won t break from this behavior   Conclusions So it seems that if you are certain that your input will not include a negative number  then it is almost twice as fast to use is int and ctype digit to validate that you have an integer  Using Method 1 with a fallback to method 5 when the variable is a string and the first character is a dash is the next fastest  especially when a majority of the input is actual integers or positive numbers in a string   All in all  if you need solid consistency  and you have no idea what the mix of data is coming in  and you must handle negatives in a consistent fashion  filter var  value  FILTER VALIDATE INT      FALSE wins   Code used to get the output above    u    -10    v    0    w   0   x    5    y    5c    z   1 44   function is int1  value       return  is int  value     ctype digit  value       function is int2  value        return   string  int  value     string  value      function is int3  value        return  strval intval  value       strval  value       function is int4  value        return  ctype digit strval  value        function is int5  value        return filter var  value  FILTER VALIDATE INT      FALSE     function is int6  value       return  is int  value     ctype digit  value      is string  value   amp  amp   value 0       -   amp  amp  filter var  value  FILTER VALIDATE INT       FALSE       start   microtime TRUE   for   i 0   i  lt  125000   i        is int1  u     is int1  v     is int1  w     is int1  x     is int1  y     is int1  z      stop   microtime TRUE    start2   microtime TRUE   for   j 0   j  lt  125000   j        is int2  u     is int2  v     is int2  w     is int2  x     is int2  y     is int2  z      stop2   microtime TRUE    start3   microtime TRUE   for   k 0   k  lt  125000   k        is int3  u     is int3  v     is int3  w     is int3  x     is int3  y     is int3  z      stop3   microtime TRUE    start4   microtime TRUE   for   l 0   l  lt  125000   l        is int4  u     is int4  v     is int4  w     is int4  x     is int4  y     is int4  z      stop4   microtime TRUE      start5   microtime TRUE   for   m 0   m  lt  125000   m        is int5  u     is int5  v     is int5  w     is int5  x     is int5  y     is int5  z      stop5   microtime TRUE      start6   microtime TRUE   for   n 0   n  lt  125000   n        is int6  u     is int6  v     is int6  w     is int6  x     is int6  y     is int6  z      stop6   microtime TRUE      time    stop -  start     time2    stop2 -  start2     time3    stop3 -  start3     time4    stop4 -  start4     time5    stop5 -  start5     time6    stop6 -  start6    print    Method 1     time  lt br gt    print    Method 2     time2  lt br gt    print    Method 3     time3  lt br gt    print    Method 4     time4  lt br gt      print    Method 5     time5  lt br gt      print    Method 6     time6  lt br gt

[php] Checking if a variable is an integer in PHP

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