Not mentioned elsewhere: intval(NULL) also returns 0.
PHP - Manual: intval
2024-12-23
intval
(PHP 4, PHP 5, PHP 7, PHP 8)
intval — 获取变量的整数值
说明
通过使用指定的进制 base 转换（默认是十进制），返回变量 value
的 int 数值。
intval() 不能用于 object，否则会产生
E_NOTICE 错误并返回 1。
参数
-
value -
要转换成 integer 的数量值
-
base -
转化所使用的进制
注意:
如果
base是 0，通过检测value的格式来决定使用的进制：- 如果字符串包括了 "0x" (或 "0X") 的前缀，使用 16 进制 (hex)；否则，
- 如果字符串以 "0" 开始，使用 8 进制(octal)；否则，
- 将使用 10 进制 (decimal)。
返回值
成功时返回 value 的 integer 值，失败时返回 0。
空的 array 返回 0，非空的 array 返回 1。
最大的值取决于操作系统。 32 位系统最大带符号的 integer 范围是 -2147483648 到 2147483647。举例，在这样的系统上，intval('1000000000000') 会返回
2147483647。64 位系统上，最大带符号的 integer 值是
9223372036854775807。
字符串有可能返回 0，虽然取决于字符串最左侧的字符。 使用 整型转换 的共同规则。
范例
示例 #1 intval() 例子
下面的例子运行于 32 位系统上。
<?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(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
?>
注释
注意:
除非
value是一个字符串，否则base不会起作用。
参见
- boolval() - 获取变量的布尔值
- floatval() - 获取变量的浮点值
- strval() - 获取变量的字符串值
- settype() - 设置变量的类型
- is_numeric() - 检测变量是否为数字或数字字符串
- 类型转换的判别
- BCMath 任意精度数学函数
add a note
User Contributed Notes 17 notes
leon at leonidasjp dot nl ¶
5 years ago
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.
winbill at hotmail dot com ¶
11 years ago
Be careful :
<?php
$n="19.99";
print intval($n*100); // prints 1998
print intval(strval($n*100)); // prints 1999
?>
zak at php dot net ¶
21 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
"$1,000,000" will convert to 0 (the 1st character is not a valid start for a number
"80,000 leagues ..." will convert to 80
"1.4e98 microLenats were generated when..." will convert to 1.4e98
Also note that only decimal base numbers are recognized in strings.
"099" will convert to 99, while "0x99" will convert to 0.
One additional note on the behavior of intval. If you specify the base argument, the var argument should be a string - otherwise the base will not be applied.
For Example:
print intval (77, 8); // Prints 77
print intval ('77', 8); // Prints 63
Anony Moose ¶
2 years ago
As a warning, do not use this function alone for input validation.
Vulnerable example:
<?php
if(isset($_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;
}
?>
Anthony ¶
4 years ago
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
?>
Ben Laurienti ¶
16 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.
chinmay235 at gmail dot com ¶
4 years ago
<?php
echo intval("10 days"); //10
echo intval("days 10"); //0
?>
spoon_reloaded at gmail dot com ¶
13 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"
?>
Anonymous ¶
2 years ago
PHP 7.2
$test = intval(150.20*100); //15019
$test2 = intval(15020); //15020
$test3 = intval(15020.0); //15020
$test4 = 150.20*100; //15020.0
espertalhao04 at hotmail dot com ¶
9 years ago
if you want to take a number from a string, no matter what it may contain, here is a good solution:
<?php
function int($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.
tuxedobob at mac dot com ¶
18 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 = $num + 0;
and PHP will leave your number alone; it'll just know it's a number. Such is the fun of a loosely-typed language. :)
mkamerma at science dot uva dot nl ¶
16 years ago
As addendum, the "if ($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).
pfreet at gmail dot com ¶
9 years 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
yves ¶
11 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.
taylorsarrafian at gmail dot com ¶
6 years ago
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 );
}
?>
simon at npkk dot cz ¶
16 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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