intval

(PHP 4, PHP 5)

intvalGet the integer value of a variable

Opis

int intval ( mixed $var [, int $base = 10 ] )

Returns the integer value of var, using the specified base for the conversion (the default is base 10). intval() should not be used on objects, as doing so will emit an E_NOTICE level error and return 1.

Parametry

var

The scalar value being converted to an integer

base

The base for the conversion

Zwracane wartości

The integer value of var on success, or 0 on failure. Empty arrays return 0, non-empty arrays return 1.

The maximum value depends on the system. 32 bit systems have a maximum signed integer range of -2147483648 to 2147483647. So for example on such a system, intval('1000000000000') will return 2147483647. The maximum signed integer value for 64 bit systems is 9223372036854775807.

Strings will most likely return 0 although this depends on the leftmost characters of the string. The common rules of integer casting apply.

Przykłady

Przykład #1 intval() examples

The following examples are based on a 32 bit system.

<?php
echo intval(42);                      // 42
echo intval(4.2);                     // 4
echo intval('42');                    // 42
echo intval('+42');                   // 42
echo intval('-42');                   // -42
echo intval(042);                     // 34
echo intval('042');                   // 42
echo intval(1e10);                    // 1410065408
echo intval('1e10');                  // 1
echo intval(0x1A);                    // 26
echo intval(42000000);                // 42000000
echo intval(420000000000000000000);   // 0
echo intval('420000000000000000000'); // 2147483647
echo intval(428);                   // 42
echo intval('42'8);                 // 34
echo intval(array());                 // 0
echo intval(array('foo''bar'));     // 1
?>

Notatki

Informacja:

The base parameter has no effect unless the var parameter is a string.

Rejestr zmian

Wersja Opis
5.1.0 Throws E_NOTICE and returns 1, when an object is passed to var.

Zobacz też:

add a note add a note

User Contributed Notes 34 notes

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19
spoon_reloaded at gmail dot com
5 years ago
Here is a really useful undocumented feature:

You can have it automatically deduce the base of the number from the prefix of the string using the same syntax as integer literals in PHP ("0x" for hexadecimal, "0" for octal, non-"0" for decimal) by passing a base of 0 to intval():

<?php
echo intval("0x1a", 0), "\n"; // hex; prints "26"
echo intval("057", 0), "\n"; // octal; prints "47"
echo intval("42", 0), "\n"; // decimal; prints "42"
?>
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10
zak at php dot net
14 years ago
intval converts doubles to integers by truncating the fractional component of the number.

When dealing with some values, this can give odd results.  Consider the following:

print intval ((0.1 + 0.7) * 10);

This will most likely print out 7, instead of the expected value of 8.

For more information, see the section on floating point numbers in the PHP manual (http://www.php.net/manual/language.types.double.php)

Also note that if you try to convert a string to an integer, the result is often 0.

However, if the leftmost character of a string looks like a valid numeric value, then PHP will keep reading the string until a character that is not valid in a number is encountered.

For example:

"101 Dalmations" will convert to 101

"$1,000,000" will convert to 0 (the 1st character is not a valid start for a number

"80,000 leagues ..." will convert to 80

"1.4e98 microLenats were generated when..." will convert to 1.4e98

Also note that only decimal base numbers are recognized in strings.

"099" will convert to 99, while "0x99" will convert to 0.

One additional note on the behavior of intval.  If you specify the base argument, the var argument should be a string - otherwise the base will not be applied.

For Example:

print intval (77, 8);   // Prints 77
print intval ('77', 8); // Prints 63
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8
Ken
2 years ago
Not mentioned elsewhere: intval(NULL) also returns 0.
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8
winbill at hotmail dot com
3 years ago
Be careful :

<?php
$n
="19.99";
print
intval($n*100); // prints 1998
print intval(strval($n*100)); // prints 1999
?>
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1
nlong121 at gmail dot com
3 months ago
As a note using intval() as a check for string comparison will not work

$string="Pork";
$test=intval($string);
echo $test.'=='.$string;
if($string==$test)
    {
    echo '::Test PASS';   
    }else{
    echo '::Test FAIL';   
    }
if(is_numeric($string))
    {
    echo '::Test PASS';   
    }else{
    echo '::Test FAIL';   
    }
/*Produces
0==Pork :: Test PASS
is_numeric(Pork) :: Test FAIL
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3
simon at npkk dot cz
8 years ago
Still have on mind, that if you convert big numbers by adding zero, PHP makes automatic "to a float" conversion, so it is same as floatVal(). So if the number is realy big (over 13 digits), you can lose preciosity. Do not use it for such long numbers, if all bits do matter (IPv6 addresses and similar).
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3
espertalhao04 at hotmail dot com
1 year ago
if you want to take a number from a string, no matter what it may contain, here is a good solution:

<?php
function int($s){return(int)preg_replace('/[^\-\d]*(\-?\d*).*/','$1',$s);}

echo
int('j18ugj9hu0gj5hg');
//output: 18
?>
this example returns an int, so it will follow the int rules, and has support for negative values.

<?php
function int($s){return($a=preg_replace('/[^\-\d]*(\-?\d*).*/','$1',$s))?$a:'0';}

echo
int('j-1809809808908099878758765ugj9hu0gj5hg');
//output: -1809809808908099878758765
?>

this one returns a string with just the numeric value.
it also supports negative values.

the latter is better when you have a 32 bit system and you want a huge int that is higher than PHP_MAX_INT.
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4
mkamerma at science dot uva dot nl
8 years ago
As addendum, the "if ($int > 0)" check in the encode function is redundant. It doesn't do anything bad to keep it in since it will always be true when reaching that point, but it's a meaningless conditional this way. It's a remnant from when I tried to write the function in terms of bitshifts, which could lead to negative ints when shifting if the 32nd bit was set (instead of always padding with 0's when using >> it pads with 1's leading to negative ints).
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3
Robin Y. Millette http://rym.waglo.com
11 years ago
Rob_Kohr at no_need_to_email dot me dot com
11-Nov-2002 12:24    

[snip]

$var=intval("122.5");
//$var==122

This is nice if you want to turn a double into an int automatically rounding down

Hum, I had a bug earlier today, involving ===. Coming from a c++ background, I can't help testing for types. I was using floor() to get an integer from a division by 2, and comparing that to a known integer from a for loop. Well, first I changed the === to == because the test would always be false otherwise. Next, I looked up this function, and converted most of my floor() calls to intval() calls, because I really meant to get an int, and not a float with no decimal part. So I have to disagree with the editor note here. Oh, and I'm comfortably back to using ===.
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3
pfreet at gmail dot com
1 year ago
Do not use intval() when you really want round(). This is due to how PHP handles precision.

echo number_format(8.20*100, 20), "<br />";
echo intval(8.20*100), "<br />";
echo floor(8.20*100), "<br />";
echo round(8.20*100), "<br />";

819.99999999999988631316
819
819
820
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2
Seally
6 years ago
Re: nobodyisperfect88 at hotmail dot de
jay at w3prodigy dot com had it right. I believe it is an issue with the floating point registers on computers, which have a precision of about 17 digits. When you get more precise than that, it rounds.

Since the second example can fit in the register, no rounding occurs, and PHP can truncate the portion after the decimal. However, the system automatically rounds the first example to 1, which is what PHP returns.

(Tested on Windows XP 32bit)
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2
yves
3 years ago
The behaviour of intval() is interesting when supplying a base, and you better check your intval base-based expressions, as it is counter-intuitive.
As the example shows
<?php
  intval
('42', 8); // => 34
 
intval(42, 8);   // => 42 !
?>
PHP considers the 42 as being already an integer, and doesn't apply any conversion. And supplying
<?php
  intval
(49, 8);  // => 49 !
?>
produces no error and no warning.
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1
mkamerma at science dot uva dot nl
8 years ago
When you need to work with integer values that exceed maxint, the following functions may be of use to you - they form a codec pair for integers of variable length rather than fixed length, encoded in a byte as a 7 bit numberal with a 1 bit has-more flag, indicating that the next byte encodes a higher order part of the same number still.

<?php
/* encode integer as 7bit with has-more bit numeral,
    ordered lowest byte first. */
function encode_7bhm($int) {
  if (
$int==0) return chr(0); // shortcut
 
$ret = "";
  while(
$int != 0) {
   
$high = floor($int / 128);     // overflow for this round
   
$low = $int - ($high * 128); // 7 bit numeral
   
if ($int > 0) {
      if (
$high > 0) { $low = $low + 128; } // has-more flag
     
$ret .= chr($low); } //encode
   
$int = $high// set overflow as next round's number
 
}
  return
$ret;
}

/* decode a 7bit with has-more bit numeral,
    ordered lowest byte first. */
function decode_7bhm($hmb) {
 
$ret = 0;
 
$pos = 0;
 
$high = 1;
  while(
$high == 1) {
   
$byte = ord(substr($hmb, $pos, 1));
   
$high = floor($byte/128); // gets has-more flag
   
$low = $byte - ($high*128);
   
$ret += $low * pow(128, $pos++); // decode
 
}
  return
$ret;
}
?>

This codec pair is also quite useful when needing to write ints to files, as this is a low-numeral biased encoding: most of the time this will only require 8 or 16 bit rather than the 32 bits an int will use in fixed-length encoding.

The encoding range:

  1 byte  - 0 through 128 (2^7)
  2 bytes - 129 through 16,384 (2^14)
  3 bytes - 16,385 through 2,097,152 (2^21)
  4 bytes - 2,097,153 through 268,435,456 (2^28)

while indeed a 32 bit encoded variable length integer will be lower than maxint, rather than needing a new 32 bit block to represent higher range only 8 more bits are required to represent this higher number (for completeness the range of representation by bytes 5-8 are listed):

  5 bytes - 268,435,457 through 34,359,738,368 (2^35)
  6 bytes - 343,59,738,369 through 4,398,046,511,104 (2^42)
  7 bytes - 4,398,046,511,105 through 562,949,953,421,312 (2^49)
  8 bytes - 562,949,953,421,313 through 720,57,594,037,927,936 (2^56)

Also for completeness, the function to read a 7 bit with has-more bit from a filepointer:

<?php
// read a 7bhm numeral from file
function read_7bhm($fp) {
 
$bytestring = "";
 
$high = 1;
  while(
$high==1) {
   
$byte = fread($fp, 1);
   
$high = floor(ord($byte)/128); // check for has-more bit
   
$bytestring .= $byte;
  }
  return
decode_7bhm($bytestring); }
?>
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1
anonymous at place dot com
8 years ago
re: Disturbing issue with intval()

It's probably just good practice to round decimals anyways.  i.e...

$amount = round(19.99 * 100);
$test2 = intVal($amount);
$test3 = intVal("$amount");

echo $test2 . "<br />\n";
echo $test3 . "<br />\n";
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0
jplevene at netscape dot net
9 months ago
I have found intval very useful for database security.

If you are passing a value via

- Data from user input
- Data that you have stored RAW on DB (witch is the best way) and you are using on a new sql statment
- Data from unknown/other origin

and the data is supposed to be an integer, I always run it through intval before I put it into the query (or you could use real_escape_string)

This prevents hackers from passing the variable as an SQL statement instead of a number in order to attack your database.
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0
bert at nospam dot thinc dot nl
5 years ago
If you need the reverse function of intval(), the code hereunder might be helpfull.

<?php
function itoa( $ii, $radix=10, $stritoa="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabc" ) {
    if (
$radix > strlen( $stritoa ) )    //    does request makes sense?
       
return "";    //    think of your own way to handle this case
   
$sign = $ii<0 ? "-": "";
   
$ii = abs( $ii );
   
$rc = "";
    do {
       
$rc .= $stritoa[ $ii % $radix ];
       
$ii = floor( $ii / $radix );
        } while (
$ii >0 );
    return
$sign . strrev( $rc );
    }
?>
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0
phpben hood id au
6 years ago
kris at mha dot ca:

Implicit typing. This is a feature, not a bug.

The == operator will convert your string to an int automatically (in this case) so that it is really comparing 123 and 123, which is of course the same.

If you use the === operator then this will not occur, as it will only match on the same value and type. This works as expected:

<?php

$tmp_array
= "123,232,141";

if (
intval($tmp_array) === $tmp_array)
{
    echo
"'".intval($tmp_array)."' equals '$tmp_array'\n";
}
else
{
    echo
"'".intval($tmp_array)."' does not equal '$tmp_array'\n";
}

?>
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0
aryel at redtwilightNO dot comSPAM dot brNOT
7 years ago
Since integers are stored on multiple bytes in the memory in binary format, once an signed long integer reaches the maximum value of 2147483646 (which is the maximum value that 8 bits of memory, size of a long int, can store, binary-wise), atleast on C/C++ the number starts to roll back, going gradually to ...45, ...45 and eventually reaching a negative value. Some REALLY large values will return -1, probably because PHP simply rejects the number, though I'm not sure why.

For further info:
http://www.rwc.uc.edu/koehler/comath/13.html
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0
Ben Laurienti
8 years ago
You guys are going to love this.  I found something that I found quite disturbing.

$test1 = intVal(1999);

$amount = 19.99 * 100;
$test2 = intVal($amount);
$test3 = intVal("$amount");

echo $test1 . "<br />\n";
echo $test2 . "<br />\n";
echo $test3 . "<br />\n";

expected output:
1999
1999
1999

actual output
1999
1998
1999

Appears to be a floating point issue, but the number 1999 is the only number that I was able to get to do this.  19.99 is the price of many things, and for our purpose we must pass it as 1999 instead of 19.99.
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0
Anonymous
10 years ago
When trying to read 32bit values (32 bit limitation depends on the word size of your machine)  from a string that is represented in hex with the high bit set,
eg. F9833234

intval returns -1. The reason is the sign bit being set. This number is larger than can be saved in a signed int.

The way around this is to read the value in using two calls to intval.

eg.

$val = intval(substr($str,0,4), 16); // read high 16 bit word
$val <<= 16; // shift hi word correct position
$val |= intval(substr($str, 4, 4), 16); //  read low 16 bit word
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0
tuxedobob at mac dot com
10 years ago
Sometimes intval just won't cut it. For example if you want to use an unsigned 32-bit int and need all 32 bits. Recently, I wrote a little script that took and integer and converted it to an IP address. After realizing I couldn't just mod the whole thing, since the sign bit throws it off (and compensating for that), we ran into a problem where if it was entered into a form, the value somehow wasn't converted to an integer properly, at least not implicitly. The solution for this, and the way I recommend converting a string to an integer, is:

$num = $num + 0;

and PHP will leave your number alone; it'll just know it's a number. Such is the fun of a loosely-typed language. :)
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-1
jeremy at cfegames dot com
4 years ago
When retrieving numbers or integers from a MySQL DB, it's best to use intval(), or it will continue to be a string.

<?php
while($row = mysql_fetch_array($check)
{
$_SESSION['id'] = inval($row['id']);
$user_id = intval($_SESSION['id']); // Not sure if you need to do it again, but doesn't hurt.
}

is_int($_SESSION['id'])
is_int($user_id)
is_string($_SESSION['id'])
is_string($user_id)

// Output
true
true
false
false
?>
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-1
gregrobson at gmail dot com
2 years ago
I just wanted to be sure that a string was going to be valid if I intval'ed it. This regular expression matches:
0
Any positive integer (no + sign)
Any negative integer (with a - sign)

It does not match a leading 0 or any other character. You are advised to strip out commas, trim the string and check range yourself ;)

<?php
/**
* Loops through each non-array element and actions a function.
*
* @return boolean|integer TRUE if the value matches as an integer, FALSE if
* an error occured or 0 if not match was found.
*/
public function validate($value)
{
   
$value = preg_match('/^(0|(-{0,1}[1-9]\d*))$/', trim($value));

    if (
$value == 1)
        return
true;
    else
        return
$value;
}
?>

If you use intval() now, you are merely changing the data type.
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-1
lrdsatyr8 at hotmail dot com
6 years ago
If you just want to get the integer value of a number without all the hassle, just use intval()... like so:

$a1 = 10.4;
$a2 = -12.5;
$a3 = 44.1238503;

print intval($a1);   // returns 10
print intval($a2);   // returns -12
print intval($a3);   // returns 44

it's that easy!
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-1
maciek dot iwanowskis at glasspartnership dot co dot uk
7 years ago
It seems that if you're trying to cast to integer (or use intval()) on integer of value bigger then 2147483646 it's hard to predict returned value.
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-1
simon at npkk dot cz
8 years ago
intval() returns maxint on number_in_string, if the result would be bigger than it. But for float returns the signed 32 bit integer with the "same" value:
<?php
$num
=-1000;
print(
$num."\n");
$i_str=sprintf("%u",$num);
print(
$i_str."\n");
$i1=intval($i_str);
print(
$i1."\n");
$i2=intval(floatval($i_str));
print(
$i2."\n");
?>

prints:

-1000
4294966296
2147483647
-1000
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-1
ittasks at gmail dot com
5 years ago
when converting some optional form values to positive integers and to be on the safe side, you can use this:

<?php $q=intval("0".$_REQUEST['q']); ?>
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-1
jazeik at gmail dot com
7 years ago
@kris:
If you had followed the following links:
"The common rules of integer casting apply." => http://us.php.net/manual/en/language.types.integer.php
"See String conversion to numbers" => http://us.php.net/manual/en/language.types.integer.php

Then you would have found the following: "The value is given by the initial portion of the string. If the string starts with valid numeric data, this will be the value used."

So this behaviour is a feature not a bug.

The following code will work:
<?php

$tmp_array
= str_replace(",", "", "123,232,141");

if(
intval($tmp_array) == $tmp_array){
    echo
intval($tmp_array) . " equals $tmp_array\n";
}else{
    echo
intval($tmp_array) . " does not equal $tmp_array\n";
}

?>

Output:
123232141 equals 123232141
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-2
adspeed.com
9 years ago
Say you have a string $s="3763328634" to be used as a key into the database, intval() this string will result in a different,smaller number (depends on the machine/OS). To keep the number intact but as an int/long type, do $s +=0; instead.
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-3
jay at w3prodigy dot com
6 years ago
Note:

$int = 0.99999999999999999;
echo intval($int); // returns 1

and

$int = 0.9999999999999999;
echo intval($int); // returns 0
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-4
michiel ed thalent nl
6 years ago
A function to get an integer from everywhere in a string (concatenated or not).

<?php
function str2int($string, $concat = true) {
   
$length = strlen($string);   
    for (
$i = 0, $int = '', $concat_flag = true; $i < $length; $i++) {
        if (
is_numeric($string[$i]) && $concat_flag) {
           
$int .= $string[$i];
        } elseif(!
$concat && $concat_flag && strlen($int) > 0) {
           
$concat_flag = false;
        }       
    }
   
    return (int)
$int;
}
echo
var_dump(str2int('sh12apen11')); // int(12)
echo var_dump(str2int('sh12apen11', false)); // int(1211)
echo var_dump(str2int('shap99en')); // int(99)
echo var_dump(intval('shap99en')); // int(0)
?>
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-6
Anonymous
8 years ago
Operating on integers gives puzzling results--which don't seem to have to do with the number of bits...

<?php
echo intval(1e10);  // -1 on my system; 1410065408 in the example
echo intval(1e5); // 100000 (my own example: lower number--works all right)
echo intval(4e9);  // -294967296 ! (my own example: somewhere in the middle)

echo intval(42000000);  // 42000000 (as in the manual; reasonable)
echo intval(420000000000000000000);  // -1 on my system at least. 0 in the example
// ...and yet still odder...
echo intval(4200000000);  // -94967296! (my own example: somewhere in between)
?>
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-5
yhoko at yhoko dot com
6 years ago
Note that this function behaves different in PHP4/5 when parsing NAN-values. Try the following example:

<?php die( "Result = " . intval( NAN ) ); ?>

- In PHP 4 the result is 0
- In PHP 5 the result is 2^31 (running on 32bit)

Yhoko
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-7
vizigr0u at gmail dot com
7 years ago
intval used on bools returns either 1 or 0
I usually use this to properly set bools in my tables
(assuming you use some kind of int like tinyints as booleans) :
<?php
$myvar
= 'right value';
mysql_query('INSERT INTO mytable (activated)
VALUES('
. intval($myvar === 'right value') . ')');
?>
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