Not mentioned elsewhere: intval(NULL) also returns 0.
(PHP 4, PHP 5, PHP 7, PHP 8)
intval — 変数の整数としての値を取得する
指定された値 base を基数（デフォルトは 10）とする、
value の int としての値を返します。
オブジェクトに intval() を使用することはできません。
その場合は E_WARNING レベルのエラーを発して 1 を返します。
value整数に変換するスカラー値
base変換のための基数
注意:
baseが 0 の場合は、valueのフォーマットに基づいて利用する基数を決めます。
- 文字列の先頭が "0x" (あるいは "0X") の場合は、基数を 16 (十六進数) とします。
- 文字列の先頭が "0b" (あるいは "0B") の場合は、基数を 2 (二進数) とします。
- 文字列の先頭が "0" の場合は、基数を 8 (八進数) とします。
- それ以外の場合は、基数を 10 (十進数) とします。
成功時は value の整数値、失敗時は 0。
空の配列の場合は 0、空でない配列の場合は
1 を返します。
最大値はシステムに依存します。32 ビットシステムでは、
最大の符号付き整数の範囲 -2147483648 ～ 2147483647 となります。
このため、そのようなシステムでは intval('1000000000000')
は 2147483647 を返します。
64 ビットシステムにおける最大の符号付き整数は 9223372036854775807
となります。
文字列の場合、文字列の最左の文字に依存しますが、ほとんどの場合で 0 を返します。 整数への変換 の一般的なルールが適用されます。
例1 intval() の例
以下の例は 64 ビットシステムに基づきます。
<?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); // 10000000000
echo intval('1e10'); // 10000000000
echo intval(0x1A); // 26
echo intval('0x1A'); // 0
echo intval('0x1A', 0); // 26
echo intval(42000000); // 42000000
echo intval(420000000000000000000); // -4275113695319687168
echo intval('420000000000000000000'); // 9223372036854775807
echo intval(42, 8); // 42
echo intval('42', 8); // 34
echo intval(array()); // 0
echo intval(array('foo', 'bar')); // 1
echo intval(false); // 0
echo intval(true); // 1
?>注意:
パラメータ
baseはパラメータvalueが文字列でない限り意味がありません。
Be careful :
<?php
$n="19.99";
print intval($n*100); // prints 1998
print intval(strval($n*100)); // prints 1999
?>It seems intval is interpreting valid numeric strings differently between PHP 5.6 and 7.0 on one hand, and PHP 7.1 on the other hand.
<?php
echo intval('1e5');
?>
will return 1 on PHP 5.6 and PHP 7.0,
but it will return 100000 on PHP 7.1.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 63You 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 $test3 . "<br />\n";
expected output:
1999
1999
1999
actual output
1999
1998
1999
Appears to be a floating point issue, but the number 1999 is the only number that I was able to get to do this. 19.99 is the price of many things, and for our purpose we must pass it as 1999 instead of 19.99.Here is a really useful undocumented feature:
You can have it automatically deduce the base of the number from the prefix of the string using the same syntax as integer literals in PHP ("0x" for hexadecimal, "0" for octal, non-"0" for decimal) by passing a base of 0 to intval():
<?php
echo intval("0x1a", 0), "\n"; // hex; prints "26"
echo intval("057", 0), "\n"; // octal; prints "47"
echo intval("42", 0), "\n"; // decimal; prints "42"
?>if you want to take a number from a string, no matter what it may contain, here is a good solution:
<?php
function int($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.The binary notation is NOT supported until php7.2
<?php
// PHP <7.2 | PHP >=7.2
echo intval(0b11); // 3 | 3
echo intval(-0b11); // -3 | -3
echo intval('0b11'); // 0 | 0
echo intval('-0b11'); // 0 | 0
echo intval('0b11', 0); // 0 | 3
echo intval('-0b11', 0); // 0 | -3
?>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 = $num + 0;
and PHP will leave your number alone; it'll just know it's a number. Such is the fun of a loosely-typed language. :)As a warning, do not use this function alone for input validation.
Vulnerable example:
<?php
if(isset($_GET['id']) && intval($_GET['id']) > 0){
echo $id;
}
?>
The following requests would pass this filter:
/page.php?id=10
/page.php?id=10oops
/page.php?id=10<script>alert(1)</script>
/page.php?id=1' OR '1'='1
/page.php?id[]=<script>alert(1)</script>
Instead use the is_numeric() function for integer validation:
<?php
echo intval("10oops"); // 10
echo is_numeric("10oops"); // false
?>
Secure example:
<?php
if(isset($_GET['id']) && is_numeric($_GET['id']) && intval($_GET['id']) > 0){
echo $id;
}
?>PHP 7.2
$test = intval(150.20*100); //15019
$test2 = intval(15020); //15020
$test3 = intval(15020.0); //15020
$test4 = 150.20*100; //15020.0Do 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
820The 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.beware:
<?php
// observe the following
echo intval( strval( -0.0001 ) ); // 0
echo intval( strval( -0.00001 ) ); // -1
// this is because
echo strval( -0.0001 ); // -.0001
echo strval( -0.00001 ); // -1.0E-5
// thus beware when using
function trunc2_bad( $n ) {
return intval( strval( $n * 100 ) / 100 );
}
// use this instead
function trunc2_good( $n ) {
return intval( floatval( strval( $n * 100 ) ) / 100 );
}
?>As addendum, the "if ($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).Warning: intval() parses scientific notation, like "12.3e7".
This comes out of the blue when you use intval() to cut the first integer value from a string; at first glance there's nothing wrong with it, if you have "123.jeff" it will give you 123, but in the rare case of parsing something that has a second segment with a hex number, you can easily run into this. (Let's not start the "why would you parse a string like that" argument.)
So if you're not prepared, these results may surprise you:
intval("123.ee-2") - gives you 123
intval("123.e2-e") - gives you 12300
intval("123.a2-e") - gives you 123
intval("123.e-22") - gives you 0
intval("123.e-a2") - gives you 123
intval("123.e-2a") - gives you 1
intval("123.2e2a") - gives you 12320
intval("123.22e2") - gives you 12322
intval("123.22ea") - gives you 123
Again, this is somewhat expected behaviour once you know that scientific notation is interpreted by it. But it looks like a less-than-widely known fact and I only faced this issue after 20+ years of php.