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    intval

    (PHP 4, PHP 5, PHP 7, PHP 8)

    intval — 获取变量的整数值

    说明

    intval(mixed $value, int $base = 10): int

    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_WARNING 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 "0b" (或 "0B") 开头，使用 2 进制 (binary)；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。

    更新日志

    版本 说明
    8.0.0 对象转换时的错误级别已从 E_NOTICE 更改为 E_WARNING。

    示例

    示例 #1 intval() 例子

    下面的例子运行于 64 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); // 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
    ?>

    注释

    注意:

    除非 value 是一个字符串，否则 base 不会起作用。

    参见

    add a note add a note

    User Contributed Notes 16 notes

    up
    336
    Ken
    13 years ago
    Not mentioned elsewhere: intval(NULL) also returns 0.
    up
    143
    winbill at hotmail dot com
    13 years ago
    Be careful :

    <?php
    $n    ="19.99";
    print     intval($n*100); // prints 1998
    print intval(strval($n*100)); // prints 1999
    ?>
    up
    69
    leon at leonidasjp dot nl
    7 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.
    up
    50
    zak at php dot net
    24 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
    up
    35
    Ben Laurienti
    18 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.
    up
    38
    spoon_reloaded at gmail dot com
    15 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"
    ?>
    up
    5
    Anonymous
    4 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
    up
    7
    Anthony
    6 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
    ?>
    up
    13
    espertalhao04 at hotmail dot com
    11 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.
    up
    5
    Anony Moose
    4 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;
    }
    ?>
    up
    7
    tuxedobob at mac dot com
    20 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. :)
    up
    5
    mkamerma at science dot uva dot nl
    18 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).
    up
    6
    pfreet at gmail dot com
    11 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
    up
    1
    taylorsarrafian at gmail dot com
    9 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 );
       }

    ?>
    up
    2
    yves
    13 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.
    up
    1
    Denes Kellner
    9 months ago
    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.
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